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1
Wiest, Anthony D. "Thermal cycling behavior of unidirectional and cross-plied P100 Gr/6061 aluminium composites." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/24071.
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Approved for public release; distribution is unlimitedThe thermal strain response of as-cast samples of 40% PI 00 graphite fiber reinforced 6061 Al composites in the unidirectionally reinforced and the [0/90] cross-plied configuration was studied. Thermal strain hysteresis and residual plastic strain were observed, both changing with continued cycling. The compressive residual plastic strain is attributable primarily to creep deformation due to compressive residual stress in the matrix at elevated temperature. The role of matrix creep in the heating rate dependence of the strain response was studied by measuring strains under isothermal conditions in the absence of applied stresses. Damage mechanisms operative in the composites during thermal cycling, and the impact of ply constraint on the strain response were also evaluated.
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Salvo, Luc. "Comportement au durcissement structural de matériaux composites à matrice aluminium renforcée de particules céramiques : cas des systèmes 6061/SIC et 6061/Al2O3." Grenoble INPG, 1992. http://www.theses.fr/1992INPG0064.
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Nous avons entrepris une etude systematique sur le durcissement structural de materiaux composites a matrice metallique renforces de particules ceramiques sur deux plans: la precipitation et le comportement en durete. Tout au long de cette etude, nous nous sommes attaches a comparer le comportement a la precipitation et au durcissement structural des cmm avec la matrice non renforcee suivant la temperature de revenu principalement. Dans la matrice comme dans les cmm, une temperature critique, delimitant deux domaines de precipitation, a ete mise en evidence. La cinetique de precipitation est toujours acceleree dans les cmm par rapport a la matrice non renforcee, d'autant plus que la fraction volumique de renforts est importante. Ces resultats sont interpretes en terme de germination et croissance des precipites differentes dans les cmm du fait de la presence d'une forte densite de dislocations. L'etude de l'evolution comparee de la durete en fonction du temps de revenu des composites et de la matrice non renforcee indique qu'en dessous de la temperature critique, les cinetiques de durcissement des materiaux sont semblables, alors qu'au-dessus, les composites presentent un maximum de durete plus tot. Ces effets sont correles a l'etat de precipitation
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Rekik, Wissal. "Etude de la ténacité d'une soudure en undermatch : Application à la tenue mécanique de la jonction soudée FE en Al 6061-T6." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2016. http://www.theses.fr/2016ESMA0015/document.
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Dans le cadre de la démonstration de l’intégrité des composants nucléaires les plus sensibles, une analyse de la présence d’un défaut potentiel de type fissure peut être requise par la sureté nucléaire. Ceci est particulièrement le cas en présence de jonctions soudées. Pour assurer un conservatisme de cette analyse, la position du défaut postulé doit être la plus pénalisante possible. Les analyses réalisées pour des démonstrations similaires sur des structures en acier reposent sur une approche de type mono matériau utilisant le comportement du métal de base. Cette approche est la plus pénalisante dans le cas d’une soudure en overmatch mais doit être remise en cause dans le cas d’une soudure en undermatch. Dans ce cadre, cette thèse propose une méthodologie expérimentale et numérique permettant l’identification de la configuration la plus pénalisante vis-à-vis de la mécanique de la rupture d’une soudure en undermatch. L’application de cette méthode a été réalisée sur une soudure en faisceau d’électrons en Al6061-T6. Un gradient de propriétés mécaniques le long de la jonction soudée a été dans un premier temps identifié permettant la conduite d’une analyse fine basée sur une approche multimatériau. Dans un second temps, le comportement en ténacité de la jonction soudée a été étudié sur éprouvettes CT. La transférabilité du paramètre J à l’amorçage à une autre géométrie d’éprouvette a été démontrée ce qui constitue une base importante pour l’hypothèse de transférabilité vers des structures. Pour finir, une étude numérique sur un tube de grandes dimensions avec un défaut semi-elliptique a été développée en prenant en compte les contraintes résiduelles de soudage. Les résultats montrent que la zone affectée thermiquement à 13 mm du centre de la soudure considérée est la plus sensible en mécanique de la rupture, ceci remet par conséquent en question les méthodes traditionnelles menées dans des analyses à la rupture brutale qui consistent à considérer un défaut dans la zone fondueFor the demonstration of the integrity of the most sensitive nuclear components, conventional defects, as cracks for example, must be considered within the design step as required by the nuclear safety authority. This phase is particularly crucial for dimensioning of welded structures. To ensure a conservative prediction, the position of the initial crack within the welded joint must be the most detrimental in fracture behavior. Commonly used analyzes consider homogeneous structure with the behavior of the base metal of the welded joint, considered as the weakest metallurgical zone in the case of an overmatched weld. In contrast, similar analysis is not conservative in case of undermatched weld. The thesis contributes by the development of an experimental and numerical methodology allowing the identification of the detrimental metallurgical zone in fracture behavior of an undermatched welded joint. The methodology proposed is applied to an electron beam welded joint on Al 6061-T6. To reach this goal, the gradient of the mechanical behavior along the welded joint was first identified. This is particularly interesting to conduct an advanced analysis based on a multimaterial approach. In a second step, the fracture behavior of the welded joint was studied on CT specimen. The transferability of the J integral at initiation was approved on another geometry: this represents an important foundation for the transferability assumption to structure. Finally, a numerical analysis on full scale tube was developed. Residual welding stresses and structural effects were considered. The results demonstrate that the heat affected zone located at 13 mm from the middle of the welded joint is the most detrimental zone for fracture analysis. This contradicts the conventional methods conducted on fracture analysis which consider a conventional defect within the fusion zone
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Béal, Maxime. "Compréhension et maîtrise de la mise en œuvre par fabrication additive (LPBF) d'un alliage d'aluminium à basse teneur en silicium pour l'aéronautique." Electronic Thesis or Diss., Ecully, Ecole centrale de Lyon, 2022. http://www.theses.fr/2022ECDL0026.
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La fabrication additive devenant de plus en plus mature a montré sa capacité à être une technologie de rupture en matière d’innovation industrielle. En effet, la fabrication additive permet d’obtenir une pièce quasi fonctionnelle à partir d’un fichier 3D. La fusion laser sur lit de poudre (Laser Powder Bed Fusion - LPBF) est l’un des procédés de fabrication additive. La société Thales® est très fortement intéressée par ce type de procédé et souhaite le développement du LPBF pour accentuer sa compétitivité sur le marché aéronautique. Un alliage d’aluminium a été développé pour le procédé LPBF et breveté par Thales en 2019. Les travaux de thèse présentés dans ce manuscrit ont comme objectif de poursuivre les travaux menés sur cet alliage et de faciliter le processus d’industrialisation de celui-ci par le procédé LPBF pour des pièces destinées à l’aéronautique et l’aérospatiale. Le manuscrit est divisé en 4 parties, la première traitant de la bibliographie et des méthodes utilisées. La deuxième partie aborde l’interaction laser matière et l’optimisation de la rugosité. La partie numéro trois traite du cycle de vie de la poudre en analysant l’effet de la réutilisation et du stockage sur le procédé. Enfin la quatrième et dernière partie aborde l’optimisation de la composition chimique de l’alliage et la recherche d’un traitement thermique adapté. L’optimisation de l’interaction laser a montré la relation entre les paramètres utilisés et la géométrie des bains de fusion formés. Il a également été montré qu’il était plus difficile de mettre en oeuvre l’alliage 6061-Zr qu’un alliage d’aluminium de fonderie type Al-Si. Ce chapitre a également mis en lumière le phénomène de focal shift et l’importance de l’altitude plateau impactant fortement le procédé. Par la suite une optimisation de la rugosité a été effectuée en appliquant des contours. Un très bon état de surface est obtenu, néanmoins, cette méthode a été éprouvée sur des géométries plus complexes que des cubes et a montré ces faiblesses. Le traitement de la poudre a ensuite été abordé. La réutilisation de la poudre conduit à une hausse du taux d’oxygène et une modification chimique de la poudre. Le tamisage est essentiel pour garantir la granulométrie et éviter ces phénomènes. Le stockage des poudres est critique pour les applications visées. En effet, le stockage tel que réalisé dans cette étude a montré un fort impact sur le procédé réduisant la densité, l’allongement et la résilience des pièces tout en dégradant l’état de surface. Le brevet concernant le 6061-Zr étant assez large, le taux de Zirconium a été optimisé afin de répondre le plus possible au cahier des charges tout en évitant le phénomène de fissuration à chaud. Par la suite, des traitements thermiques ont été appliqués sur des alliages comportant différents taux de Zirconium afin d’observer l’impact de ces traitements en fonction de la température, de la durée et de la présence plus ou moins importante de Zirconium. L’ensemble de ces résultats a permis de lever des verrous scientifiques et facilite ainsi la progression de cette technologie vers une industrialisation maîtrisée pour des applications aéronautiques et spatialesAdditive manufacturing is becoming more and more mature and has shown its capacity to be a disruptive technology in terms of industrial innovation. Indeed, additive manufacturing allows to obtain a functional part from a 3D file. Laser Powder Bed Fusion (LPBF) is one of the additive manufacturing processes. Thales® is very interested in this type of process and would like to develop LPBF to increase its competitiveness in the aeronautical market. An aluminium alloy has been developed for the LPBF process and patented by Thales in 2019. The objective of the thesis work presented in this manuscript is to continue the work carried out on this alloy and to facilitate the industrialisation process of this alloy by the LPBF process for aeronautical and aerospace parts. The manuscript is divided into 4 parts, the first one focusing on the bibliography and the methods used. The second part deals with laser-material interaction and roughness optimisation. Part three deals with the life cycle of the powder by analysing the effect of reuse and storage on the process. Finally, the fourth and last part focuses on the optimisation of the chemical composition of the alloy and the search for a suitable heat treatment. The optimisation of the laser interaction showed the relationship between the parameters used and the geometry of the molten pool formed. It was also shown that it was harder to use the 6061-Zr alloy than a cast aluminium alloy such as Al-Si alloy. This chapter also highlighted the focal shift phenomenon and the importance of the plate altitude which has a strong impact on the process. Subsequently, a roughness optimisation was carried out by applying contours. A very good surface finish was obtained, however, this method was tested on more complex geometries than cubes and showed its weaknesses. The life cycle of the powder was then discussed. The reuse of the powder leads to an increase in oxygen content and chemical modification of the powder. Sieving is essential to ensure particle size and avoid these phenomena. The storage of powders is critical for the intended applications. Indeed, storage as carried out in this study has shown a strong impact on the process reducing the density, elongation and resilience of the parts while degrading the surface finish. As the patent for 6061-Zr is quite broad, the zirconium content was optimised to meet the specifications as much as possible while avoiding hot cracking. Subsequently, heat treatments were applied to alloys with different levels of Zirconium in order to observe the impact of these treatments as a function of temperature, duration and the level of Zirconium content. All of these results helped to remove scientific obstacles and thus facilitate the progression of this technology into controlled industrialisation for aeronautical and space applications
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Shen, Yang. "Comportement et endommagement des alliages d’aluminium 6061-T6 : approche micromécanique." Thesis, Paris, ENMP, 2012. http://www.theses.fr/2012ENMP0089/document.
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L'alliage d'aluminium 6061-T6 a été retenu pour la fabrication du caisson-coeur du futur réacteur expérimental Jules Horowitz (RJH). L'objectif de cette thèse est de comprendre et modéliser le comportement et l'endommagement de cet alliage en traction et en ténacité, ainsi que l'origine de l'anisotropie d'endommagement. Il s'agit de faire le lien entre la microstructure et l'endommagement du matériau à l'aide d'une approche micromécanique. Pour ce faire, la microstructure de l'alliage, la structure granulaire et es précipités grossiers ont été caractérisés en utilisant des analyses surfaciques (Microscopie Électronique à Balayage) et volumiques (tomographie/laminographie X). Le mécanisme d'endommagement a été identifié par des essais de traction sous MEB in-situ, des essais de tomographie X ex-situ et des essais de laminographie X in-situ pour différents taux de triaxialité. Ces observations ont notamment permis de montrer que la germination des cavités sur les précipités grossiers de type Mg2Si est plus précoce que sur les intermétalliques au fer. Le scénario identifié et les grandeurs mesurées ont ensuite permis de développer un modèle d'endommagement couplé, basé sur l'approche locale de la rupture, de type GTN intégrant la germination, la croissance et la coalescence des cavités. Le lien entre l'anisotropie d'endommagement et de forme/répartition des précipités a pu être montré. Cette anisotropie microstructurale modifie les mécanismes : Pour une sollicitation dans le sens long l'endommagement est majoritairement intergranulaire alors que dans le sens travers on observe un endommagement mixte intergranulaire et intragranulaire. La prise en compte des mesures de l'endommagement dans la simulation a permis d'expliquer l'anisotropie d'endommagement. Ce travail servira de référence pour les études futures qui seront menées sur le matériau irradiéThe AA6061-T6 aluminum alloy was chosen as the material for the core vessel of the future Jules Horowitz testing reactor (JHR). The objective of this thesis is to understand and model the tensile and fracture behavior of the material, as well as the origin of damage anisotropy. A micromechanical approach was used to link the microstructure and mechanical behavior. The microstructure of the alloy was characterized on the surface via Scanning Electron Microscopy and in the 3D volume via synchrotron X-ray tomography and laminography. The damage mechanism was identified by in-situ SEM tensile testing, ex-situ X-ray tomography and in-situ laminography on different levels of triaxiality. The observations have shown that damage nucleated at lower strains on Mg2Si coarse precipitates than on iron rich intermetallics. The identified scenario and the in-situ measurements were then used to develop a coupled GTN damage model incorporating nucleation, growth and coalescence of cavities formed by coarse precipitates. The relationship between the damage and the microstructure anisotropies was explained and simulated
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Flament, Camille. "Etude des évolutions microstructurales sous irradiation de l'alliage d'aluminium 6061-T6." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI074/document.
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L’alliage d’aluminium 6061-T6 a été choisi comme matériau de structure du casier et du caisson du cœur de réacteur Jules Horowitz (RJH). Transparent aux neutrons, il doit ses bonnes propriétés mécaniques à la précipitation de fines aiguilles nanométriques appelées béta'' contenant Mg et Si et à la présence de dispersoïdes Al(Cr,Fe,Mn)Si jouant un rôle important dans la résistance à la recristallisation. Le caisson et le casier seront soumis à de forts flux neutroniques à une température avoisinant les 50°C. L’objectif de cette thèse est d’étudier les évolutions microstructurales de l’alliage sous irradiation et plus particulièrement la stabilité des précipités. Pour cela, des études analytiques par irradiations in-situ et ex-situ aux électrons et aux ions à température ambiante et forte dose ont été réalisées ainsi qu’une étude du comportement des précipités sous irradiations aux neutrons à faible dose. La caractérisation fine des précipités par Microscopie Electronique en Transmission a montré que les dispersoïdes sont stables sous irradiation, cependant ils présentent une structure cœur/coquille avec un cœur riche en (Fe, Mn) et une coquille riche en Cr qui s’accentue sous irradiation par accélération de la diffusion. En revanche, les nano-phases type béta’’ sont déstabilisées par l’irradiation. Elles sont dissoutes par irradiation aux ions au profit de l’apparition d’amas riches en Mg, Si, Al, Cu et Cr participant à l’augmentation du durcissement de l’alliage, tandis qu’elles tendent à se transformer en précipités cubiques sous irradiation aux neutronsThe 6061-T6 Aluminium alloy, whose microstructure contains Al(Fe,Mn,Cr)Si dispersoids and hardening needle-shaped beta” precipitates (Mg, Si), has been chosen as the structural material for the core vessel of the Material Testing Jules Horowitz Nuclear Reactor. Because it will be submitted to high neutron fluxes at a temperature around 50°C, it is necessary to study microstructural evolutions induced by irradiation and especially the stability of the second phase particles. In this work, analytical studies by in-situ and ex-situ electron and ion irradiations have been performed, as well as a study under neutron irradiation. The precipitates characterization by Transmission Electron Microscopy demonstrates that Al(Fe,Mn,Cr)Si dispersoids are driven under irradiation towards their equilibrium configuration, consisting of a core/shell structure, enhanced by irradiation, with a (Fe, Mn) enriched core surrounded by a Cr-enriched shell. In contrast, the (Mg,Si) beta” precipitates are destabilized by irradiation. They dissolve under ion irradiation in favor of a new precipitation of (Mg,Si,Cu,Cr,Al) rich clusters resulting in an increase of the alloy’s hardness. beta’’ precipitates tend towards a transformation to cubic precipitates under neutron irradiation
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Benoit, Alexandre. "Développement du soudage MIG CMT pour la réparation de pièces aéronautiques. Application aux pièces en alliage base aluminium 6061." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112308/document.
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Cette étude répond à une demande industrielle de réparation d’une pièce aéronautique en alliage d’aluminium 6061 à l’aide d’un procédé de soudage à l’arc. La première partie est consacrée à la comparaison des procédés Metal Inert Gas (MIG), MIG pulsé, Tungsten Inert Gas et MIG Cold Metal transfer (CMT). C’est ce dernier procédé qui a été sélectionné pour ses aptitudes particulières, comme son bon contrôle des paramètres et le faible endommagement produit dans le métal de base. Puis, deux métaux d’apport ont été testés – les alliages 5356 et 6061 – avec deux stratégies de réparation : le soudage et le rechargement. Les résultats d’essais mécaniques ont démontré que le rechargement avec l’aluminium 5356 est l’option la plus adaptée pour cette application. Les essais sur pièce réelle ont prouvé la pertinence de cette approche.La zone affectée thermiquement générée, dans l’alliage 6061, par les procédés de soudage à l’arc a également été caractérisée. Il a été mis en évidence une variation de la microstructure associée aux changements de propriétés mécaniques de cette zone. Enfin, les essais exploratoires de soudage homogène à l’arc, c’est-à-dire, avec le métal d’apport en 6061, ont prouvé qu’il était possible, dans certaines conditions, de souder sans générer de fissuration, bien que, cet aluminium soit réputé comme étant insoudable de cette manièreThis study responds to an industrial demand of repair using an arc welding process. It concerns an aeronautical piece made in 6061 aluminium alloy. The first part of the study is devoted to the comparison of processes Metal Inert Gas (MIG), pulsed MIG, Tungsten Inert Gas and MIG Cold Metal Transfer (CMT). It is the latter process that was selected for its special abilities, such as its good control of parameters and the low damaging produced in the base metal. Then, two filler alloys were tested – 5356 and 6061 aluminium alloys– with two repairing strategies : welding and building up. The results of mechanical tests showed that building up with aluminum 5356 is most suitable option for this application. The trials on the real piece showed the relevance of this approach.The heat affected zone generated by the arc welding process in the 6061 base metal was also characterized. It was shown a varaition of microstructure associated with the change of mechanical properties in this zone. Finally, exploratory trials of homogeneous arc welding, i.e., with the 6061 filler alloy showed that it was possible, with certain conditions, to weld without generating weld cracking, although, this aluminium is deemed unweldable by this way
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Jalali, Alireza. "Performance of minimum quantity cooling (MQC) when turning aluminium alloy 6061-T6 : surface roughness, tool temperature and aerosol emission." Mémoire, École de technologie supérieure, 2013. http://espace.etsmtl.ca/1206/1/JALALI_Alireza.pdf.
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Aujourd'hui, les industries désirent réaliser la meilleure finition de surface et un taux élevé d'usinage. Ces facteurs sont utilisés pour évaluer la performance des processus d'usinage. Lorsque le taux d'enlèvement de matière augmente lors de l'usinage, la température de l'outil s’élève aussi et le refroidissement devient nécessaire.
Pour réduire les effets de la chaleur sur les outils de coupe et la durée de vie des machines, une application efficace et rentable du fluide de coupe est nécessaire. En outre, pour faire face aux questions environnementales et de sécurité au travail, les nouvelles méthodes de lubrification et de refroidissement telles que la quantité minimale de lubrifiant (MQL) et la quantité minimale de refroidisseur (MQC) ont été proposées.
L'usinage presque sec ou microlubrifiée avec la quantité minimale de refroidisseur ou de lubrifiant (MQCL), fournit une diminution considérable de la consommation de fluide de coupe par rapport à un refroidissement conventionnel ainsi que l'augmentation de l'usinabilité en comparaison avec d'usinage complètement à sec. La rugosité de surface, la réduction de la chaleur générée dans l'outil de coupe et l'émission de la poussière et d'aérosols dans l'atelier, comme un indicateur de la qualité du processus d'usinage, dépendent largement des conditions d'usinage.
La présente recherche sorte sur l'étude des effets des différentes conditions de coupe, en utilisant de la quantité minimale de refroidisseur, sur la rugosité de surface, la température de l'outil de coupe et la concentration des aérosols et des poussières lors du tournage d'alliage d'aluminium 6061-T6. Les résultats sont comparés a ceux obtenus en tournage à sec et ceux obtenus en tournage sous lubrification abondante. Il est trouvé qu'il y a des conditions optimales pour lesquelles l’usinage MQC donne de meilleur fini de surface que l’usinage à sec et l’usinage sous lubrification abondante; l’usinage MQC et l’usinage à lubrification abondante produisent plus d’aérosols (liquide et solide) comparé à l’usinage à sec; et enfin, l’usinage MQC refroidit moins la coupe que l’usinage lubrifié traditionnel. Cependant l’usinage MQC demeure préférable en raison de la réduction des risques pour la sécurité du travail et pour l’environnement.
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Petit, Tom. "Compréhension et modélisation d’essais de ténacité avec pop-in : application à l’aluminium 6061-T6 et influence de l’irradiation neutronique." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM019/document.
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Le pop-in est un phénomène d’instabilité de propagation de fissure observé lors d’essais de ténacité sur certains matériaux. Ce phénomène a été observé sur l’alliage d’aluminium 6061-T6 qui a été identifié pour constituer des éléments de structure essentiels du cœur du réacteur de recherche Jules Horowitz. Cette thèse a été initiée pour comprendre l’origine de ce phénomène sur l’aluminium 6061-T6 et en proposer une modélisation à bases physiques qui pourra être utilisée pour l’exploitation et l’interprétation des essais de ténacité, notamment à l’état irradié.Les différentes pistes identifiées dans la littérature ont été testées expérimentalement. Des revenus (4/8/12/16 h) ont été appliqués afin d’obtenir différents comportements mécaniques. Des essais de traction avec corrélation d’images ont montré que les pop-ins observés ne sont pas dus à un effet PLC. Ils ne correspondent pas non plus à une hétérogénéité microstructurale ; ils ne sont pas liés à des mécanismes d’endommagement, car la rupture est typiquement ductile, qu’un pop-in soit intervenu ou non. Ces mécanismes et les différentes microstructures ont été comparés par le biais de plusieurs techniques (MEB, EBSD, EDS, Sonde Atomique Tomographique, tomographie, laminographie et nanolaminographie par rayonnement synchrotron). Les pop-ins sont donc uniquement le résultat d’une accélération de la rupture ductile.En réalité, ils sont dus à une interaction entre deux paramètres : une résistance réduite du matériau à la propagation de fissure (i.e. un faible module de déchirement) et une complaisance importante du dispositif d’essai (i.e. une faible raideur). Afin d’investiguer ce deuxième paramètre, un dispositif innovant a été conçu, permettant de faire varier la raideur de la machine d’essai lors d’essais de ténacité. Deux critères analytiques, l’un basé sur la courbe force-ouverture, l’autre sur l’intégrale J, ont été établis, permettant de quantifier les conditions d’amorçage et d’arrêt de pop-in de façon fiable.Pour prendre en compte le rôle central du durcissement vis-à-vis de la propagation ductile, un nouveau critère de germination piloté par les contraintes a été introduit dans un unique modèle GTN. Cela permet de simuler et de reproduire par éléments finis les différentes courbes de ténacité J-Δa en modifiant uniquement la loi élastoplastique. En rajoutant des ressorts dans les modélisations et avec un pilotage adapté, les pop-ins sont simulés avec succès, et restent exploitables avec les critères analytiques.Des études sur éprouvettes irradiées réalisées dans des enceintes blindées ont montré que l’augmentation des pop-ins avec l’irradiation résultait de la diminution du module de déchirement, elle-même due au durcissement. De même qu’à l’état non irradié, les pop-ins apparaissent donc à cause de l’interaction du module de déchirement avec le dispositif d’essai, et non pas à cause d’une gamme d’élaboration industrielle non maitriséePop-in is a phenomenon of crack propagation instability observed during toughness tests on some materials. This phenomenon has been observed on the 6061-T6 aluminum alloy, which has been identified as an essential structural element of the core of the Jules Horowitz research reactor. This thesis was initiated to understand the origin of this phenomenon on 6061-T6 aluminum and to propose a physics-based modeling, usable for the exploitation and interpretation of toughness tests, especially in the irradiated state.The different origins identified in the literature have been experimentally tested. Different aging times (4/8/12/16h) were applied to obtain different mechanical behaviors. Tensile tests with image correlation have shown that the observed pop-ins are not due to a PLC effect. Nor do they correspond to microstructural heterogeneity; they are not linked to different fracture mechanisms, because the rupture is typically ductile, whether a pop-in is involved or not. These mechanisms and the different microstructures were compared using several techniques (SEM, EBSD, EDS, Atom Probe Tomography, tomography, synchrotron laminography and nanolaminography). Pop-ins are therefore only the result of an acceleration of the ductile fracture.In fact, they are due to an interaction between two parameters: the reduced material crack growth toughness (i.e. the low tearing modulus), and the significant compliance of the test device (i.e. the low stiffness). In order to investigate this second parameter, an innovative setup has been designed to vary the machine stiffness during toughness tests. Two analytical criteria, one based on the load-opening curve, the other on the J-integral, have been established, making it possible to reliably quantify the conditions for initiation and arrest of pop-in.To take into account the central role of hardening for ductile propagation, a new stress-controlled nucleation criterion has been introduced into a single GTN model. This makes it possible to simulate and capture by finite elements the various J-Δa toughness curves by modifying only the elastoplastic law. By adding springs in the models and with an adapted control, the pop-ins are successfully simulated, and remain exploitable with the analytical criteria.Studies on irradiated specimens carried out in hot cells have shown that the increase in pop-ins with irradiation results from the decrease in the tearing modulus, itself due to hardening. As in the non-irradiated state, pop-ins thus appear solely because of the interaction between the tearing modulus and the test device stiffness, and not because of a range of industrial development not mastered
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Arshad, Saad. "Single Point Incremental Forming : A study of Forming Parameters, Forming limits and Part accuracy of Aluminium 2024, 6061 and 7475 alloys." Thesis, KTH, Industriell produktion, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103006.
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Nowadays there is an increasingly demanding need for the development of agile manufacturing techniques that can easily be adaptable to a constant introduction of new products in the market. Single point incremental forming (SPIF) is a new innovative and feasible solution for the rapid prototyping and the manufacturing of small batch sheet parts. The process is carried out at room temperature (cold forming) and requires a CNC machining centre, a spherical tip tool and a simple support to fix the sheet being formed. This work studied the effects of step size, angle, spindle speed, and feed rate on the forming limits of Aluminium alloys namely AA 2024, AA 6061 and AA 7475 in soft annealed condition. The Study also includes measuring the strain path and determination of maximum forming limit angles for the above mentioned alloys. This thesis provides a better understanding of the influence of rotating tool in the occurrence of fracture without previous necking or fracture following previous necking. Surface and geometric accuracy of the parts manufactured was also studied and comparisons were made between the CAD files and the actual manufactured parts and then corrections were made accordingly. The main contribution of this thesis to Single stage SPIF was the successful manufacturing of a Cone shaped parts with almost vertical walls.
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Hafley, Johanna L. "A comparison of the aging kinetics of a cast alumina-6061 aluminum composite and a monolithic 6061 aluminum alloy." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26927.
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Electrical resistivity and hardness measurements were conducted during isothermal aging treatments of an alumina particulate reinforced 6061 aluminum metal matrix composite and a monolithic 6061 aluminum control material. Transmission electron microscopy was utilized to examine the microstructural changes accompanying the changes in the resistivity of the monolithic during aging. In addition, differential scanning calorimetry was used to investigate the growth kinetics and thermal stability of the metastable phases in the control sample. From DSC experiments, the heats of formation of the metastable phases were determined as functions of aging time and temperature. These results were used to characterize the aging behavior of the matrix material. Keywords: Aluminum composite, Conductivity, Aluminum alloys. (jes)
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Strauss, Jon. "Specular reflectance of anodized 6061-T6 aluminum alloy." Kansas State University, 2012. http://hdl.handle.net/2097/15173.
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Master of ScienceDepartment of Chemical Engineering
John Schlup
This study investigated the specular reflectance properties of 6061-T6 aluminum alloy anodized in accordance with military specification MIL-A-8625 as a function of both etch process time and anodization process potential. Both process parameters affect the specular reflectance characteristics when measured using a 660 nm, collimated diode laser source. The etch process time, when varied between 0.5 to 20 minutes, resulted in a decrease in specular reflectivity with increasing time. The anodization process potential was varied between 10 and 21 volts, with a 15 volt condition producing samples with the greatest specular reflectivity. Between the two parameters, the etch time had the greater effect. Additionally, the dependence of the incident beam angle on specular reflectivity was shown not to have a significant effect when compared to the etch process time and process potential.
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Robert, Sundström. "High cycle fatigue properties of extruded 6060-T6, 6063-T6 and 6082-T6 : Influence of die lines and microstructure on fatigue in flat extruded aluminum profiles." Thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235406.
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Aluminum alloys are of great importance in the automotive and truck industries due to the weight savings that they can help to achieve. However, the use of such alloys in applications where they are subjected to alternating stresses requires knowledge about their fatigue behavior. Moreover, extrusion induces a strong texture and microstructural heterogeneity in the material and gives a surface with long grooves parallel to the extrusion direction (ED), so-called die lines. This anisotropy in surface conditions and microstructure may affect the fatigue properties. To investigate how die lines and microstructure affects fatigue in aluminum, the high cycle fatigue properties cycles of three peak-aged AlMgSi alloys were evaluated. Flat profiles of 6060-T6, 6063-T6 and 6082-T6 were tested in uniaxial stress (R = 0.1) in a servo-hydraulic fatigue testing machine with a constant stress amplitude. Two specimen types were tested for 6063 and 6082: one with the ED parallel to the loading direction (longitudinal), and one with the ED perpendicular to it (transverse). It was found that both 6063 and 6082 displayed anisotropy in fatigue lives, with the longitudinal orientation performing better. The anisotropy was far stronger in 6082 than in 6063. Furthermore, 6060 longitudinal displayed higher fatigue strength than 6063 longitudinal at higher stress amplitudes, but lower fatigue strength at lower amplitudes. Metallographic investigations with SEM indicated that grain boundaries of the surface-layer grains were involved in the initiation of the fatigue crack. Intergranular crack propagation and separation was observed on the fracture surfaces, especially in the surface layer. The extruded surfaces also showed evidence of intergranular crack propagation. The exact sites of crack initiation could not be found so it could not be proven conclusively that die lines were sites of crack initiation in transverse specimens, but there were some indications from metallographic and macrofractographic investigations that this was the case.Aluminiumlegeringar används mycket i bilindustrin på grund av de viktbesparingar som kan åstadkommas. Användandet av sådana legeringar i tillämpningar där det utsätts för cykliska laster kräver dock kunskap om deras utmattningsbeteende. Dessutom skapar extrusionsprocessen en stark textur och heterogenitet i mikrostrukturen och resulterar i en yta med fina fåror parallella med pressriktningen, s.k. die lines. Anisotropin i ytbeskaffningen och mikrostrukturen kan påverka utmattningshållfastheten. För att undersöka hur die lines och mikrostruktur påverkar utmattningen i aluminium testades högcykelutmattningsegenskaperna hos tre toppåldrade AlMgSi legeringar. Platta profiler av 6060-T6, 6063-T6 och 6082-T6 testades i enaxlig dragspänning (R = 0.1) i en servohydraulisk utmattningsmaskin med konstant lastamplitud. Två sorters provstavar testade av 6082 och 6063: en med pressriktningen parallell med lastriktningen (längsriktning) och en med pressriktningen vinkelrät mot lastriktningen (tvärriktning). Både 6063 och 6082 uppvisade olika utmattningsliv beroende på pressriktningens orientering mot lastriktningen, där längsriktningen hade längre utmattningsliv för båda legeringarna. Anisotropin var mycket starkare in 6082 än 6063. Dessutom uppvisade 6060 i längsriktningen högre utmattningsstyrka än 6063 vid höga lastamplituder, men lägre utmattningsstyrka vid lägre lastamplituder. Metallografiska undersökningar med SEM indikerade att korngränser i ytlagret var involverade i sprickinitieringen. Spricktillväxt i och separation av korngränser observerades på brottytorna, speciellt i ytlagret. Den extruderade ytan visade också bevis för interkristallin spricktillväxt. De exakta platserna för sprickinitering kunde inte hittas så det kunde inte entydigt bevisas att sprickinitieringen skedde i die lines i provstavar med pressriktningen vinkelrät mot lastriktningen, men i metallografiska och fraktografiska undersökningar fanns vissa indikationer att så var fallet.
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Juras, Josselin Renee. "Optimization of Three Machining Parameters for Micromilling on Aluminum 5052, Aluminum 6061, and Aluminum 7075." Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1620985012654821.
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Gates, Wende Sue. "Constitutive equations for hot working of aluminum alloy 6061." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/49573.
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Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Bibliography: leaf 12.
by Wende Sue Gates.
B.S.
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Marroquin, Salvador Michael Deivi. "Hypervelocity Impact of Spherical Aluminum 2017-T4 Projectiles on Aluminum 6061-T6 Multi-Layered Sheets." Thesis, Mississippi State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10642662.
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With the growing threat of orbital debris impacts to space structures, the development of space shielding concepts has been a critical research topic. In this study, numerical simulations of the hypervelocity impact response of stacked aluminum 6061-T6 sheets were performed to assess the effects of layering on penetration resistance. This work was initially motivated by set of experimental tests where a stack of four aluminum sheets of equal thickness was observed to have a higher hypervelocity ballistic resistance than a monolithic aluminum sheet with the same total thickness. A set of smoothed particle hydrodynamic simulations predicted a 40% increase in the ballistic limit for a 6-layer target compared to a monolithic sheet. In addition, the effect of variable sheet thickness and sheet ordering on the impact resistance was investigated, while still maintaining a constant overall thickness. A set of thin layers in front of a thick layer generally lead to a higher predicted ballistic limit than the inverse configuration. This work demonstrates an increase in the performance of advanced space shielding structures associated with multi-layering. This suggests that it may be possible to dramatically improve the performance of such structures by tailoring the material properties, interfaces, and layering concepts.
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Allen, Benjamin William. "Creep and Elevated Temperature Mechanical Properties of 5083 and 6061 Aluminum." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/52630.
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With the increasing use of aluminum in naval vessels and the ever-present danger of fires, it is important to have a good understanding of the behavior of aluminum at elevated temperatures. The aluminum samples 5083-H116 and 6061-T651 were examined under a variety of loading conditions and temperatures. Tensile testing was completed on both materials to measure strength properties of elastic modulus, yield strength, and ultimate strength as well as reduction of area from room temperature to 500 deg C taking measurements every 50 deg C. These tests showed how much the material weakened as temperature increases. Low temperatures had a minimal effect on strength while exposure to temperatures between 200 and 300 deg C had the most significant impact. Creep testing was also completed for these materials. These tests were completed at temperatures between 200 and 400 deg C in 50 deg C increments. Stresses for these tests were in the range of 13 to 160MPa for 5083 aluminum and between 13 to 220MPa for 6061 aluminum. These tests showed a significant relationship between stress and temperature and how changes to one can cause a very different resulting behavior. In addition to the creep testing, three creep models were examined as a means of predicting creep behavior. These models included a power law, exponential, and hyperbolic-sine versions and were able to predict creep results with decent accuracy depending on the stress used in the model.Master of Science
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Allen, Susan Marie. "Effect of alumina particle additions of the aging kinetics of 6061 aluminum matrix composites." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA238052.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 1990.Thesis Advisor(s): Dutta, I. "June 1990." Description based on title screeen viewed on October 15, 2009. DTIC Descriptor(s): Scanning, aging(materials), composite materials, growth(general), thermal stability, phase, particles, aluminum oxides, electrical resistance, kinetics, hardness, metastable state, isotherms, calorimetry, protective treatments, addition, measurement DTIC Indicator(s): Aluminum matrix composites. Author(s) subject terms: Aluminum matrix composites. Includes bibliographical references (p. 54-56). Also available in print.
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Angélico, Cristiano [UNESP]. "Soldagem TIG-AC onda retangular: efeitos da velocidade de soldagem sobre as propriedades mecânicas da Liga AA 6063-T6." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/96488.
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Neste trabalho foram investigados os efeitos da velocidade de soldagem no comportamento mecânico em juntas da liga AA 6063-T6, soldadas pelo processo TIG-CA com onda retangular desbalanceada. Foram analisadas as características macroestruturais (diluição do metal de base e coeficiente de forma). O planejamento experimental contemplou a utilização de metal de adição (AWS ER 4043), chanfro em v (60º), e variações nos parâmetros de ajuste de onda retangular nominalmente: amplitude de corrente negativa e tempo de polaridade negativa do eletrodo. A análise microestrutural utilizou microscopia ótica e microscopia eletrônica de varredura em observações no metais de solda obtidos e correspondentes ZTA. A avaliação mecânica foi realizada por meio de ensaios de tração nas juntas soldadas e medidas de microdureza Vickers. Adicionalmente, foram medidas as temperaturas máximas alcançadas nas juntas durante a soldagem. Os resultados mostram alterações nos valores das diluições do metal de base e na configuração geométrica dos cordões, em função da variação na velocidade de soldagem. As microestruturas desenvolvidas nos meios de solda e ZTA não se diferenciaram significativamente e, por consequencia, o comportamento mecânico detectado foi similar em todas as condições de soldagem aplicadas
In this study were investigated the welding speed effects in the mechanical behavior in welded joints of AA 6063-T6 alloy, welded by TIG-CA process with retangular wave. Were analyzed characteristics macrostructural (base material dillution, width and depth) of the weld bead. The experimental planning used and addition metal (AA 4043 alloy), bevel type v (60º) and variations in the setting parameter of retangular wave called negative current amplitude and duration of negative electrode polarity. The microstructural analysis used optical microscopy and scanning electron microcopy observation in the weld metals and HAZ obtained. The mechanical evaluation was performed by a tensile test on welded joints and Vickers microhardness measurements. In addition, it was measure the maximum temperature reached in during welding. The results show market changes in the values of the dillutions tested and the geometric configuration of the weld beads, mainly due to the variation in the welding speed. The microstuctures developed in the weld meal and HAZ did not differ significantly and, consequently, the mechanical behavior detected was similar in all welding conditions applied
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Angélico, Cristiano. "Soldagem TIG-AC onda retangular : efeitos da velocidade de soldagem sobre as propriedades mecânicas da Liga AA 6063-T6 /." Bauru : [s.n.], 2012. http://hdl.handle.net/11449/96488.
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Orientador: Gilberto de Magalhães Bento GonçalvesBanca: Sérgio Rodrigues Barra
Banca: Yukio Kobayashi
Resumo: Neste trabalho foram investigados os efeitos da velocidade de soldagem no comportamento mecânico em juntas da liga AA 6063-T6, soldadas pelo processo TIG-CA com onda retangular desbalanceada. Foram analisadas as características macroestruturais (diluição do metal de base e coeficiente de forma). O planejamento experimental contemplou a utilização de metal de adição (AWS ER 4043), chanfro em "v" (60º), e variações nos parâmetros de ajuste de onda retangular nominalmente: amplitude de corrente negativa e tempo de polaridade negativa do eletrodo. A análise microestrutural utilizou microscopia ótica e microscopia eletrônica de varredura em observações no metais de solda obtidos e correspondentes ZTA. A avaliação mecânica foi realizada por meio de ensaios de tração nas juntas soldadas e medidas de microdureza Vickers. Adicionalmente, foram medidas as temperaturas máximas alcançadas nas juntas durante a soldagem. Os resultados mostram alterações nos valores das diluições do metal de base e na configuração geométrica dos cordões, em função da variação na velocidade de soldagem. As microestruturas desenvolvidas nos meios de solda e ZTA não se diferenciaram significativamente e, por consequencia, o comportamento mecânico detectado foi similar em todas as condições de soldagem aplicadas
Abstract: In this study were investigated the welding speed effects in the mechanical behavior in welded joints of AA 6063-T6 alloy, welded by TIG-CA process with retangular wave. Were analyzed characteristics macrostructural (base material dillution, width and depth) of the weld bead. The experimental planning used and addition metal (AA 4043 alloy), bevel type "v" (60º) and variations in the setting parameter of retangular wave called "negative current amplitude and duration of negative electrode polarity". The microstructural analysis used optical microscopy and scanning electron microcopy observation in the weld metals and HAZ obtained. The mechanical evaluation was performed by a tensile test on welded joints and Vickers microhardness measurements. In addition, it was measure the maximum temperature reached in during welding. The results show market changes in the values of the dillutions tested and the geometric configuration of the weld beads, mainly due to the variation in the welding speed. The microstuctures developed in the weld meal and HAZ did not differ significantly and, consequently, the mechanical behavior detected was similar in all welding conditions applied
Mestre
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Morgado, Norbert. "Tréfilage à chaud de l'aluminium 6060 : nouvelle méthodologie d'identification du comportement tribologique." Valenciennes, 2003. http://ged.univ-valenciennes.fr/nuxeo/site/esupversions/38039928-2561-413f-987a-d3f0fe90893f.
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L'étude proposée s'appuie sur le procédé instrumenté de tréfilage à chaud de l'aluminium. Ce procédé est analysé d'un point de vue thermomécanique afin de dégager l'importance des paramètres d'interface dans la maîtrise du procédé. Les paramètres prépondérants sont le coefficient de frottement et le coefficient de transfert thermique entre le fil et la filière. La mise en place d'un nouveau banc d'essai permet d'identifier ces paramètres. Le banc, équipé d'un système de chauffage par induction et d'un système hydraulique asservi, permet de reproduire au plus près les conditions de contact thermomécaniques rencontrées en mise en forme à chaud. Une méthodologie multi niveaux, s'appuyant sur l'exploitation des résultats issus du banc, est présentée. Celle-ci permet de répondre à diverses attentes en terme d'optimisation de procédé, de caractérisation de conditions de frottement, d'analyse de défauts de surface (collage) ou de détermination de lois tribologiquesThe proposed study is based on the specific hot wire drawing process of aluminium. This process is thermomechanically analysed in order to point out the importance of interface parameters in the process control. The main parameters are the friction coefficient and the heat transfer coefficient. A new test device is developed to evaluate them. This test is made of a heating induction system and a servo-hydraulic system. It allows to reproduce accurately the thermomechanical contact conditions observed in hot metal forming. A multi level methodology, using exploitation of test device results, is presented. It allows to optimize the process, to identify friction conditions, to analyse surface damages (sticking) or to estimate tribological laws
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Nisarantaraporn, Ekasit. "Microstructural development and pressure requirements in 6063 aluminium alloy tube extrusion." Thesis, Imperial College London, 1995. http://hdl.handle.net/10044/1/7274.
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Narsimhachary, D. "Effect of laser welding parameters on 6061 aluminium alloy." Thesis, 2014. http://ethesis.nitrkl.ac.in/5659/1/D.Narsimhachary_611MM301_M.Tech_(R)_Thesis.pdf.
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Aluminium alloys are widely used in aircraft industry which involves a large number of joint configurations, traditionally fabricated by riveting. Disadvantages of riveting are extra weight to the structure, stress concentration, crevices corrosion and loosening due to vibrations. Moreover, it is a time consuming and manpower intense task. Laser welding can be a potential tool which is superior to other joining techniques, such as, arc welding due its heat input nature and related microstructural effect.The present study is focused on improving metallurgical and mechanical characteristics of aluminium alloy (6061-T6) sheet butt welds obtained by common single pass CO2 laser by refining the microstructure with extra laser pass/remelting. Initially, screening experiments were performed to enumerate the power density requirement for proper coupling of the laser beam in Gaussian as well as Donut beam profile, effect of shielding gas (He, Ar, and without shielding gas) flow rate, and welding speed which can yield stable keyhole, smooth weld surface and minimum weld defects (porosity, under bead, etc.). From the butt welded specimen, weldability of the alloy was studied in terms of joint strength, formability, fatigue and corrosion behaviour. The weld structure was verified with peak temperature and thermal profile analysis. The effect of the additional laser weld pass(bead on bead/remelting) on the existing butt weld was also studied by comparing the results of hardness, tensile tests, formability, fatigue test and corrosion study From the detailed characterization it was observed that with a particular process window only coupling of the laser with the material was possible and Helium showed best result compared to other shielding gas conditions used in the study. The microstructures revealed defect free welds and hardness data confirmed presence of heat affected zone (HAZ) and huge drop in overall hardness after welding. After post weld treatment (aging cycle) the hardness was increased marginally but base hardness could not be achieved and double bead weld showed marginally higher hardness due to finer structure. In both single and double pass welds sharp drop in tensile strength were observed due to cast structure, not availability of age hardening effect and possible micro porosity. Formability value of the welds was low compared to the base material due to the thermal strain in the welds.
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Mutombo, Faustin Kalenda. "Corrosion fatigue behaviour of 5083-H111 and 6061-T651 aluminium alloy welds." Diss., 2012. http://hdl.handle.net/2263/25838.
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In addition to being one of the highest strength non-heat treatable aluminium alloys, magnesium-alloyed wrought aluminium 5083 displays excellent corrosion resistance and good weldability. Aluminium alloy 6061, alloyed with magnesium and silicon, displays high strength, excellent formability, adequate weldability and good corrosion resistance. These aluminium alloys find application in the ship building and transport industries where 5083 is often joined to 6061 to produce welded structures such as complex I-beams and semi-hollow or hollow channels. This project aimed at characterizing the hardness, tensile properties, corrosion behaviour and fatigue properties (in air and in a 3.5% NaCl solution) of aluminium 5083 and 6061 in the as-received and welded conditions. Plates of 5083-H111 and 6061-T651 aluminium, prepared with double-V or square butt joint preparations, were joined using semi-automatic or fully automatic pulsed gas metal arc welding (GMAW). The pulsed GMAW process allows close control over the welding arc and facilitates the use of lower average heat inputs, thereby improving the bead appearance and mechanical properties. During this investigation, three filler wires were evaluated, namely magnesium-alloyed ER5183 and ER5356 aluminium, and silicon-alloyed ER4043. Hardness measurements revealed a decrease in hardness in the weld metal of the 5083-H111 welds. Dressed welds failed in the weld metal during transverse tensile testing, whereas undressed (as-welded) specimens failed at the weld toe or weld root due to the stress concentration introduced by the weld geometry. Significant softening, attributed to the partial dissolution and coarsening of strengthening precipitates and recrystallization during welding, was observed in the heat-affected zones of the 6061-T651 welds. During tensile testing, failure occurred in the heat-affected zone of all 6061 welds. Welding reduced the room temperature fatigue life of all specimens tested. In the 5083 welds, fatigue cracks initiated preferentially at gas pores, lack-of-fusion type defects and second phase particles in dressed welds, and at the stress concentration presented by the weld toes or the weld root in undressed welds. In 6061 welds, failure occurred preferentially in the softened heat-affected zone of the welds. As a result of improved control over the weld profile and a lower incidence of weld defects, fully automatic welds consistently outperformed semi-automatic welds during fatigue testing. The presence of a corrosive environment (a 3.5% NaCl solution in this investigation) during fatigue testing reduced the fatigue properties of all the samples tested. Corrosion pits formed preferentially at second phase particles or weld defects, and reduced the overall fatigue life by accelerating fatigue crack initiation. CopyrightDissertation (MSc)--University of Pretoria, 2012.
Materials Science and Metallurgical Engineering
unrestricted
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Chang, Chen-Shih, and 陳世章. "The Study of Cutting Behaviors in 6061 Aluminium Alloy Composites." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/29505079980442125143.
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碩士國立臺灣科技大學
機械工程系
91
Abstract This thesis investigated the cutting behavior of the CVDD cutting tools and AMCs. Firstly, AMCs cutting properties was evaluated by Taguchi method. Secondly, the cutting performance of CVDD cutting tools was evaluated under different cutting conditions. Optical microscope and scanning electronic microscope（SEM）were used to analyze the wear width of the CVDD cutting tools and the wear mechanism of worn surface, respectively. The type of chip formation and the conditions of built-up edge (BUE) were studied in this thesis. The results of experiment showed that the kind of cutting tools and depth of cutting (DOC) were the most important parameters effecting the cutting force in z-direction; the kind of cutting tools and feed rate were the most important parameters effecting the cutting distance; the kind of cutting tools and feed rate were the most important parameters effecting surface roughness when the cutting tools used to machine 6061/SiC AMCs. Additionally, PCD cutting tool had the best performance among the three cutting tools (PCD, CVDD and K10), the K10 cutting tool had the worst performance among all. The major wear mechanism of the CVDD and K10 cutting tools were crater wear and chipping that were cause by abrasive. Built-up edge（BUE）phenomenon was observed in all worn cutting tools. The CVDD cutting tool was formed BUE when it cutting distance up to 300 meters, and its cutting ability was failed when it up to 800 meters of cutting distance. On the contrary, the PCD cutting tool still had the excellent performance under the same cutting condition. The wear volume of the CVDD cutting tool was extended under the condition of high cutting speed and feed rate. Moreover, when the cutting speed and feed rate was up to a critical value, the cutting performance of the CVDD cutting tool decayed quickly. But, the CVDD cutting tool had a better performance under lower cutting speed and feed rate, and it wear behavior was unobvious. Additionally, the CVDD cutting tool had the better wear resistance when it used to cut the AMCs of lower SiC content.
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JUNG, LI MAO, and 李茂榮. "A Study on Sliding Wear Behaviours of 6061 Aluminium Alloy Composites." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/46799564447446998688.
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碩士國立臺灣科技大學
機械工程系
91
This work is to investigate the effects of different SiC particulate reinforcements of weight percent added into 6061 Al-alloy casting, extrusion process and aging on wear resistance performance. The wear surfaces and mechanism of specimens were observed and analyzed by OM, SEM and EDS. The experiment results show that adding SiC reinforcement into 6061 Al-alloy can dramatically promote the hardness and wear resistance performance of 6061 alloy. It can be observed that the wear resistance performance of specimens are better at higher sliding velocity than those at lower sliding velocity. Moreover, aging can promote the hardness and wear resistance performance of specimens. But, it can be seen that the wear resistance performance of specimens after aging during high load and high sliding velocity are worse greatly.
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Nieh, Tsay-Chyang, and 聶再強. "Effect of Calcium on the Aging Behavior of 6061 Aluminium Alloy." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/79360276369067208380.
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碩士國立成功大學
材料科學(工程)研究所
82
The effect of calcium on the aging behavior of 6061 alu- minium alloy was investigated by adding calcium of various contents in the alloy. Both aging temperature and aging time were changed in the aging treatment. The results show that when the addition of calcium is within 0.1wt%, the time to peak aging is delayed. When the calcium addition reaches 0.2 wt%, the peak hardness reduces substantially and the peak aging time is shortened again. It is thus suggested that the effect of calcium addition on delaying aging is effective until a critical calcium content in-between 0.1wt% and 0.2 wt%. The aging behavior will disappear when the calcium ad- dition reaches 0.3wt%. The metallugraphy and X-ray diffraction of the as-cast samples show that calcium and silicon formed CaAlSi. or CaAlSi during solidification.TEM/EDX analysis confirms the compound as CaAlSi.. According to the TEM result, the delay of aging behavior rised from two possible reasons. First,since silicon and calcium form CaAlSi., the con- centration of silicon in the matrix reduced, giving rise to a lower solute flux. Secondly, the increase of dislocation density leads to more vacancy annihilations. It redeces the effect of vacancy-assisted solute diffusion and hence causes the delay in aging behavior. Moreover, silicon clusters nu- cleated on the dislocations will relax coherence strain en- ergy around the precipitates and slow down the transforma- tion rate from G.P. zones to .beta. prime. This may be a minor factor of the delay in aging behavior. The disappearance of aging behavior should be due to the formation of mass CaAlSi.which deplets the precipitation hardening element, Si. In other words, it suppresses the precipitation of G.P. zones and .beta. prime.
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Yang, Chen-Chaeng, and 楊振昌. "Fabrication and Properties of Anodic Oxidation Film on Aluminium Alloy 6061-T6." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/78663245159755828901.
Full textAbstract:
碩士國立高雄應用科技大學
機械與精密工程研究所
98
In this paper, Our main research is focus on properties of anodic oxide film investigated about a single-step anodizing process of aluminium alloy(6061-T6) used by mixed acid (oxalic and sulphuric acid). We have discussed the influence of process parameters for anodic aluminium alloy oxide( AAAO) like film thickness, surface morphology, hardness and breakdown of voltage. And the process parameters to be discussed include: electrolyte type, concentration, temperature and operating voltage. In the post, anodizing technologies are used single acid for electrolyte such as sulfuric acid, oxalic acid and phosphoric acid. Up until recent years have switched to mixed acid or organic acid anodizing electrolyte was improved. Because mixed acid can reduce the oxide film dissolution rate, hardness increase and growth rate on film properties. So this paper will discuss and comparison the mixed acid and other single acid properties under different treatment conditions of oxalic acid, sulfuric acid and mixed acid. Anodized aluminum oxide was an amorphous pattern in our experiment, so the process parameters on the film was relatively more important. The results showed that current denisity and electrolyte temperature are important factors for properties of oxide film. Current denisity is main factor to control speed of ions reaction at barrier layer. When current density is rise to increase reaction rate and heat, Corrosion rates increases will lead to porous size and porosity increased and the film will loose. So To improve the quality of oxide film properties, how to control the reaction temperature stability and heat dissipation are key. We also found that the thickness increases will cause excessive stress to produces cracks. Using the mixed acid can change the stress cracks caused by excessive problems. The two different pore size characteristics of oxalic acid and sulfuric acid can reduce the stress accumulation rate of crack generation and heat. The results showed that under the same conditions using mixed acid were excellent than oxalic acid or sulfuric acid at same operating conditions.
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SHIE, Ming-tzung, and 謝明宗. "The Study of Process and Wear Behaviors in Powder Sintering 6061 Aluminium Alloy Composites." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/02655891901766144003.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
91
This work is to investigate the effects of the forms of reinforcement, particle size, contents and process parameters of Al alloy 6061 composites on mechanical properties and wear resistance performance. The microstructure and the micrographs of wear surface of specimens are observed and analyzed by OM, SEM and EDS. This experimental results show that there is an optimal content of fine particle reinforcement in powder sintering 6061 aluminium alloy composites. As the optimal content of reinforcement is reached, it could effectively accommodate in the porosities between the particles of matrix, causing the hardness and wear resistance performance of specimens reach the optimal status. During the wear process, the fine particle reinforcement would be removed due to the plastic deformation of matrix if overload；it would be pulled out or brittle fracture and detach form the matrix due to the coarse particle reinforcement. Moreover, the wear resistance performance of coarse particle reinforcement is superior to that of fine particle reinforcement when B4C is used as the reinforcement in the Al alloy 6061 composites.
30
Chang, Soung-Po, and 張松柏. "Reasearch 6061 aluminium alloy fatigue property of inert gas tungsten arc welding and vacuum brazing." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/13055303694539241509.
Full textAbstract:
碩士國立中央大學
機械工程研究所
100
The 6061-T6 aluminium alloy is commonly used in automobile industry, and inert gas tungsten arc (TIG) welding and vacuum brazing(VB) welding are the most popular to be applied. Nowadays, the existing regulations only focuses on the specific fatigue assessment of melting welding. As a result, the study analyzes the differences of mechanical properties of inert gas tungsten arc (TIG) welding and vacuum brazing(VB) welding through hardness test, static fatigue test, tensile test, and metallographical observation and investigates the applicability of existing regulations as well. According to the analysis of metallographical and hardness tests, the result is discovered that the influenced width of inert gas tungsten arc (TIG) welding is almost equal to the width of welding, whereas the base material of vacuum brazing(VB) welding exposes in hot environment for long time to annealing, precipitation hardening phase grows, which decreases the hardness; in the meanwhile, the material and welding diffusion layer are heated equally, so there is no obvious differences of hardness with heat affect zone of inert gas tungsten arc (TIG) welding. The breaking point of tensile and fatigue of gas tungsten arc (TIG) welding is different from the tests. The break of tensile test occurs in heat affect zone whereas it appears in the weak welding fulled with cracks in fatigue test. However, for vacuum brazing(VB) welding, the breaking points of tensile and fatigue both occur within welding diffusion layer. Since there is no significant differences of strength of the material, the damages appear within the positions where the weaknesses will grow easily. Compared with each regulation, the prediction of inert gas tungsten arc (TIG) welding is in accordance with IIW within the stress range of lower cycle 104, but the trend becomes conservative for every regulation has hugh differences between higher cycle prediction and results from experiment, and this can be seen the most from the regulation prediction assessment of Euecode 9. On the other hand, the vacuum brazing(VB) welding can be not be stable predicted since it is easily influenced by properties such as the time length of holding temperature and the fixed pressure, the quality is unstable and the statistics of fatigue is distributed differently.
31
Chen, Chi-yuan, and 陳麒元. "The research of ZrO2/Al2O3 oxide film coated on 6061 aluminium alloy by microarc discharge oxidation." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/53043241328810904119.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
102
Zirconia composite coating was prepared on 6061 aluminum alloy by microarc discharge oxidation. Tthe microstructure, hardness, XRD and toughness have been investigated in this study. First, the the experiments were carried out in alkaline electrolyte containing K2ZrF6 at different negative voltage. The results indicated that it is easier to form alumina than Zirconia for MDO coating on aluminum alloy, because Zr(OH)4 partilce were formed in alkaline easily. Compare with formation of alumina MDO coating, Zr(OH)4 partilce made a lot of pores during coating and which not uniform coating. K2ZrF6 dissolves in acidity electrolyte to prevent formation of Zr(OH)4 partilce. But the acidity electrolyte will corroded the cathode lead zirconia composite coating not to be compact. The problem of Zr(OH)4 partilce precipitation was solve by adding dispersant (NaPO3)6. There is a good experimental result that was carried out at negative voltage 100 V what XRD result indicated t-ZrO2 mainly. In order to get more compact coating, the sodium aluminate (NaAlO2) 2 g/L was added into the K2ZrF6 electrolyte. There is also a good experimental result was carried out at negative voltage 100 V and the coating was more compact than before and XRD result indicated t-ZrO2 mainly. When the contain of aluminum sodium aluminate in the K2ZrF6 electrolyte is greater than 4 g / L, the thickness and density were decreasing . Because sodium aluminate is weak alkaline, it caused the problem of Zr(OH)4 partilce precipitation when sodium aluminate is too much. XRD result indicated ??Al2O3 mainly. Above MDO result were carried by voltage control. When the coating thickness is increasing ,the current is decreasing , and than there is no energy to let coating to grow and to be more compact . In order to get more compact and more thicker coating, experiment process was change from voltage control to current control. The result show that the thickness were increase without sodium aluminate, but there were still some big pores in the coating. Better result were carried out with sodium aluminate by 0.3~0.5A in K2ZrF6 electrolyte.. And then the density were more compact by increasing contain of K2ZrF6. The voltage was limited at prosess of later stage to avoid damage from larger size of arc. XRD result indicated t-ZrO2 mainly, and the more m-ZrO2 were forming, when the contain of K2ZrF6 increasing in electrolyte. Zirconia MDO coating have higher toughness than alumina MDO coating, but it cause toughness decrease when K2ZrF6 contain too much in electrolyte . Corrosion resistance test results show that when the contain of K2ZrF6 increasing in electrolyte, the thickness and density of the coating increase , and the corrosion resistance increased. The corrosion resistance decreases due to the large pores between the surface layer and the substrate ,and the cracks were throughout the coating, when K2ZrF6 reached 22g / L.
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Geltser, Ilia Samsonovich. "Microstructural evolution during hot deformation of the 6061 aluminium alloy based Al₂O₃ metal matrix composites." Thesis, 1993. http://hdl.handle.net/2429/1366.
Full textAbstract:
The development of conventional direct casting techniques to produce aluminium alloy based metal matrix composites and the successful fabrication of these composites by extrusion and forging processing has contributed to their successful commercialization. The Center for Metallurgical Process Engineering recently initiated a collaborative research study with the Ontario Center for Materials Research to develop a mathematical model describing microstructural evolution of 6061-alumina metal matrix composite during extrusion processing. The research described in this thesis was directed at quantifying the microstructural changes associated with hot axisymmetric testing of a 6061 aluminium alloy reinforced with 10, 15 and 20% alumina particulate. Cylindrical specimens 10 mm diameter x 15 mm height were compressed in the temperature range of 573-823 K (300-550 °C), at a strain rate of 0.01-10 /s. The resulting true stress-true strain data corrected for deformation heating were used by another researcher to develop the constitutive equations for hot deformation. True local strains at different points within the heterogeneously deformed specimen were determined by metallographic measurements of the aspect ratio of the deformed grains. To reveal the aluminum grain boundaries, existing etching techniques were modified. Grain and subgrain size evolution was investigated by optical metallography. Recovery behavior of the 6061 and the composites was very similar while recrystallization behavor differed markedly. Only up to 5% fraction recrystallized was observed in the 6061 material deformed at temperatures above 723 K and annealed at the deformation temperature, while grain growth was more apparent. Deformation at 723-773 K and annealing at 798 K produced up to 8% fraction recrystallized. Five regions with different microstructural behaviour were identified for the composites: i) below 673 K recovery is sluggish and deformation flow lines persist during annealing; ii) at temperatures above 673 K at strain rates less than 0.5 /s, recovery is intensive, the optically visible subgrains form and the original grain boundaries persist during deformation; iii) at strain rates from 0.1 to 1 /s static recrystallization occurs; iv) at strain rates from 1 to 5 /s in the composites there is a region of metadynamicre crystallization; v) at strain rates above 5 /s dynamic recrystallization occurs. The mixed static/metadynamic recrystallization kinetics (static or dynamic nucleation and static growth of recrystallized grains) in the composites in the temperature range 723-788 K for strain rates of 0.5-5 /s and strains of 0.4-1.2, could be described using the Avrami equation with n=1.4 and the time for 50% recrystallisation as: t₅₀% = 3.1‧10⁻¹⁸‧έ⁻ˣ‧exp(293000/RT)‧ε⁻ⁿ ; with x~2 and n=5.3. In the region exibiting dynamic recovery, the temperature-strain rate dependence of the resulting subgrain size was determined to be dsub = -0.686+0.044‧In(Z), in good agreement with literature data. After deformation to a strain of 1, the average angle between the maximum cluster or particle dimension and the matrix flow direction was measured as 21 and 30 degrees respectively. No particle fracture, particle debonding or de-clustering was observed.
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Lin, Huei, and 林暉. "Fatigue Assessment of 6061-T6 Aluminium Alloy Joints Processed by Tungsten Inert Gas Welding and Vacuum Brazing." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/27058499239792206021.
Full textAbstract:
博士國立中央大學
機械工程學系
104
Tungsten inert gas welding and vacuum brazing butt joints and T-joints of Al–Mg–Si alloy 6061 in the artificially aged condition T6 were studied. Microhardness, tensile, constant amplitude and variable amplitude fatigue loading tests were performed. The experimental S-N curves were compared with the fatigue design curves recommended by the International Institute of Welding, British Standard, and Eurocode 9. Two mean stress correction methods, Goodman and Gerber, were evaluated. For the tungsten inert gas welding joints, the area with the lowest microhardness was the HAZ. For the vacuum brazing specimen, no clear HAZ was observed. Because the weldment was heated to a uniform temperature in a vacuum, so local overheating did not occur. In terms of the tensile properties of butt joints, the tensile strength of the vacuum brazing specimen increased with specimen thickness, whereas that of the tungsten inert gas welding welding specimen decreased. Tungsten inert gas welding butt joints and T-joints of AA 6061-T6 achieved higher fatigue strength as compared to the fatigue design curves of IIW, BS 8118, and Eurocode 9. In the lower life region (N = 104 ~ 105), it was found that the fatigue strength of vacuum brazing butt joints was lower than that of IIW FAT 45, but still higher than those of the BS 8118 class 42 and Eurocode 9 category 56-7. When tungsten inert gas welding or vacuum brazing joints of aluminum 6061-T6 was subjected to a variable amplitude loading with tensile mean stress, Goodman method was suitable to modify the mean stress effect. For T-joints, the fatigue life of the tungsten inert gas welding specimens given the bracket history can be predicted using the S-N method. The fatigue life of the vacuum brazing specimens under the bracket history can be predicted using the Goodman mean stress correction method. In terms of the size effect on the fatigue life, the thickness correction method recommended by the IIW was applicable to the tungsten inert gas welding joints of aluminum 6061-T6. This article proposed an innovational thickness correction method based on the ratio of the ultimate tensile strengths of specimens with different thickness. For butt joints of vacuum brazing, the tensile strength–based thickness correction method was better than the thickness correction methods recommended by the International Institute of Welding. For T-joints, vacuum brazing is required to carry out thickness correction in the higher life region.
34
Youseffi, Mansour, and N. Showaiter. "PM processing of elemental and prealloyed 6061 aluminium alloy with and without common lubricants and sintering aids." 2006. http://hdl.handle.net/10454/3942.
Full textAbstract:
NoA comparison has been made between compaction, sintering, microstructural and mechanical properties of the 6061 aluminium alloy prepared via premixed elemental (EL) and prealloyed (PA) powders (as received and degassed) with and without additions of sintering aids and various solid and/or liquid lubricants. Both EL and PA powders were cold pressed at different pressures, ranging from 250 to 770 MPa, and sintered under vacuum in the range 580-640°C for 30-120 min. and then under pure nitrogen atmosphere for comparison. Vacuum degassing of the PA powder provided better compressibility and thus higher green densities than those for the as received PA or the premixed EL powder compacts pressed at compaction pressures ¿340 MPa. Near full sintered densities of ~98%TD were obtained for both EL and PA 6061 Al alloys. Degassed PA Al with 0·6 wt-% paraffin wax (PW) or with only 0·12 wt-%Pb addition as sintering aid and no lubricant, and premixed EL with only 0·12 wt-%Pb addition and no lubricant gave the best optimum properties. It became apparent that additions of some solid lubricants such as lithium stearate (LS) and acrawax to both the premixed EL and PA powders provided reasonable green densities, but had deleterious effect on sintered densities and microstructures, particularly under vacuum sintering. Heating data curves during the sintering cycle, revealed formation of both transient and persistent liquid phases for the EL and mainly supersolidus liquid phase sintering (SLPS) mechanism for the PA. Tensile properties of the degassed, vacuum or nitrogen sintered PA Al alloy in T6 condition were higher than those of the equivalent alloy prepared by EL mixing with the former giving a tensile strength of 330 MPa and 6-8% elongation to failure, which are similar to those of the commercial (wrought) 6061 Al alloys.
35
Bosta, Mohannad Majid Saleem Al, and 浦和達. "The Infrared Emissivity of Ceramic Coating Produced by Micro-Arc Oxidation Process on Surface of 6061 Aluminium Alloy." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/27475208405542687687.
Full textAbstract:
博士中華大學
工程科學博士學位學程
102
ABSTRACT The high emitter surfaces enhance the thermal performance of heating and cooling systems and consequently reduce the needed energy. This study devoted to the enhancement of emissivity of 6061 aluminum alloy by microarc oxidation process (MAO). We investigated the impact parameters on the low temperature IR emissivity of MAO alumina ceramic prepared at different conditions and we found that: - In general, the MAO enhanced the IR emissivity at the whole studied wavelength range (4-16 µm). - The curve of IR emissivity has two major regions: semitransparent. 4.0- 7.6 µm, and opaque region: 8.5- 16.0 µm. - The increment of processing time from 10 min to 60 min slightly enhanced the IR emissivity at the whole studied region. - A linear correlation was found between the surface roughness and the area ratio of the volcano-like microstructure. - Both curves of voltage-time and current-time have three stages correlated with the growth of MAO ceramic layer and its properties. - For the first time, the curve of IR emissivity was analyzed by dividing it into several regions according to spectra behavior and applying the multiple linear regression (MLR) to find out the effective factors. - A new model was introduced to describe the relationship between bipolar pulsing periods (BPP) and the MAO layer thickness. Also, this model was described by contours at different levels to show up the influence of variation of BPP’s on the layer thickness. - The current density slightly enhanced the IR emissivity in the semitransparent region, but did not achieve a significant change in the opaque region. - The increment of electrolyte temperature from 12.3 °C to 90.5 °C significantly changed the MAO ceramic properties from thick layer with surface microstructure of volcano-like and accumulated particles to a thin layer which has rougher surfaces covered by grainy spherical hollow bulges microstructures with more pore density and more sillimanite and cristobalite phases which enhanced the IR emissivity and widened the opaque region. Keywords: Microarc oxidation; aluminium 6061 alloy; IR emissivity; alkaline silicate electrolyte
36
Kumar, K. "Studies On Friction Stir Welding Of Precipitation Hardenable Aluminium Alloys." Thesis, 2009. https://etd.iisc.ac.in/handle/2005/720.
Full textAbstract:
Friction Stir Welding (FSW) is an emerging solid state welding process. It has been a proven method for welding high strength aluminium alloys which were previously not recommended for conventional fusion welding. Since the invention of the process by The Welding Institute, United Kingdom, in 1991, a number of studies have been conducted on the material flow, microstructural evolution and mechanical properties of friction stir welds. However, there is not enough conceptual background available on FSW process for physical understanding of the mechanism of weld formation. In addition to that, FSW welds of high strength precipitation hardenable aluminium alloys suffer from reduced joint efficiency due to overaging in the heat affected zone. In the present investigation, experimental analysis has been carried out to understand the mechanism of weld formation and parameter optimization for aluminium alloys 7020-T6 and 6061-T6. For this purpose the investigations have been made on both the process aspects and the material aspects.
The process aspects are analyzed with the objective of learning the mechanism to produce defect free welds. For this purpose experiments have been carried out to analyze the effect of FSW parameters, material flow and the frictional characteristics between the tool and base metal. Preliminary experiments are conducted on aluminium alloy 7020-T6 with different tool geometries to analyze the interaction of the tool with the base metal using a knee-type vertical milling machine. Then, the tool geometry which produced defect-free weld is used for further experimentation. The role of tool pin, shoulder and axial load on the formation of defect free weld is analyzed in an innovative experiment, where the tool and base metal interaction is continuously increased by continuously increasing the interference between the tool and base metal. In another experiment the initial abutting interface position with respect to the tool is continuously varied to study the interaction of the tool with the initial interface and to find the positional information where the initial interface is completely eliminated. Further, the tool metal interface condition is studied using a specially designed tribological experiment which simulates the FSW condition.
From the base metal point of view, due to the strain, strain rate and temperature imposed on the base metal during the process, the microstructure is altered. In precipitation hardenable aluminium alloys the strengthening precipitates are dissolved or overaged in the weld region depending on the peak temperature in the region, which reduces the joint efficiency. However, the dissolution and overaging are kinetic process. In order to analyze this time dependant softening behavior of the base metal 7020-T6 and 6061-T6, isothermal annealing and differential scanning calorimetric studies are performed.
In order to obtain FSW welds with maximum joint efficiency, the welding temperature should not exceed the “softening temperature” of the base metal. But, to produce defect free welds favorable material flow in the weld nugget is necessary. The material flow and consolidation depend on the process temperature. Hence, for a given tool to produce defect free weld there is a need for minimum temperature. If the weld formation temperature is less than the base metal softening temperature, the weld can be made with 100% joint efficiency. In order to optimize the FSW parameter which gives defect free weld with lowest possible temperature, an instrumented programmable FSW machine is designed and developed. The machine is designed in such a way that welding parameters – rotation speed, traverse speed and plunging depth – can be continuously varied from the start to end of the weld between given two values. This reduces the number of experimental trials, material and time.
Based on the experimental results the following conclusions are derived.
1.The minimum diameter of the pin required for FSW depends on the base metal and tool material property for a given set of parameters. If the pin diameter is insufficient for a given set of welding parameters, it fails during plunging operation itself.
2.There is a minimum diameter of the shoulder for a given diameter of the pin which produces defect free weld. The ratio of pin to shoulder to produce a defect free weld is not a constant value. It changes with tool geometry and process parameters.
3.Increasing the area of contact between the tool and shoulder for a given set of parameters increases the heat input and results in increased weld nugget grain size.
4.Initial abutting interface of the base metal is eliminated at the leading edge of the tool. However, new surfaces are generated due to interaction with the tool and the newer surfaces are consolidated at the trailing edge of the tool. Importantly, the weld strength is controlled by the defects generated due the improper elimination of newly generated surfaces.
5.Optimal axial load is required to generate the required pressure to consolidate the transferred material at the trailing edge of the tool and should be equal to the flow stress of the material at the processing temperature. The optimal axial load is 8.1kN for a tool having 20mm diameter shoulder with 6mm diameter frustum shaped pin.
6.Only the material that approaches the tool at the leading edge on the advancing side is stirred and the remaining material is simply extruded around the tool. Further, the initial abutting interface is completely removed only when it is located in the stirring zone, otherwise the initial abutting interface is not eliminated. In the present study the interface is completely stirred when it is located on the advancing side of the tool between 0.5mm away from the centerline and edge of the tool.
7.The temperature and pressure at the tool–base metal interface is above the temperature and pressure required for seizure to occur for given tool material (H13) and base metal (7020-T6). Hence, it is clear that during FSW the base metal transfers on to the tool and interaction occurs between transferred layer on tool and base metal. The coefficient of friction between the given tool material and base metal in FSW condition is in the range of 1.2 – 1.4.
8.The minimum temperature requirement for FSW of 7020-T6 is 400oC and 6061-T6 is 430oC. However, 7020-T6 and 6061-T6 softens at lower temperatures than that of the minimum FSW temperature. 7020-T6 softens 30% in 7min at 250oC, 4min at 300oC, 2min at 350oC and 1min at 400oC. After softening 30%, there is 10% recovery in hardness and the hardness remains constant thereafter. Whereas 6061-T6 softens gradually up to 47% in 7min at 350oC and 400oC, below the temperature of 250oC for 7020-T6 and 350oC for 6061-T6 there is no softening observed in 7min.
9.The maximum joint efficiency of the 7020-T6 weld is 82% and 6061-T6 weld is 60%.
10. The reduction in joint efficiency is attributed to overaging of the material in the heat affected zone.
37
Kumar, K. "Studies On Friction Stir Welding Of Precipitation Hardenable Aluminium Alloys." Thesis, 2009. http://hdl.handle.net/2005/720.
Full textAbstract:
Friction Stir Welding (FSW) is an emerging solid state welding process. It has been a proven method for welding high strength aluminium alloys which were previously not recommended for conventional fusion welding. Since the invention of the process by The Welding Institute, United Kingdom, in 1991, a number of studies have been conducted on the material flow, microstructural evolution and mechanical properties of friction stir welds. However, there is not enough conceptual background available on FSW process for physical understanding of the mechanism of weld formation. In addition to that, FSW welds of high strength precipitation hardenable aluminium alloys suffer from reduced joint efficiency due to overaging in the heat affected zone. In the present investigation, experimental analysis has been carried out to understand the mechanism of weld formation and parameter optimization for aluminium alloys 7020-T6 and 6061-T6. For this purpose the investigations have been made on both the process aspects and the material aspects.
The process aspects are analyzed with the objective of learning the mechanism to produce defect free welds. For this purpose experiments have been carried out to analyze the effect of FSW parameters, material flow and the frictional characteristics between the tool and base metal. Preliminary experiments are conducted on aluminium alloy 7020-T6 with different tool geometries to analyze the interaction of the tool with the base metal using a knee-type vertical milling machine. Then, the tool geometry which produced defect-free weld is used for further experimentation. The role of tool pin, shoulder and axial load on the formation of defect free weld is analyzed in an innovative experiment, where the tool and base metal interaction is continuously increased by continuously increasing the interference between the tool and base metal. In another experiment the initial abutting interface position with respect to the tool is continuously varied to study the interaction of the tool with the initial interface and to find the positional information where the initial interface is completely eliminated. Further, the tool metal interface condition is studied using a specially designed tribological experiment which simulates the FSW condition.
From the base metal point of view, due to the strain, strain rate and temperature imposed on the base metal during the process, the microstructure is altered. In precipitation hardenable aluminium alloys the strengthening precipitates are dissolved or overaged in the weld region depending on the peak temperature in the region, which reduces the joint efficiency. However, the dissolution and overaging are kinetic process. In order to analyze this time dependant softening behavior of the base metal 7020-T6 and 6061-T6, isothermal annealing and differential scanning calorimetric studies are performed.
In order to obtain FSW welds with maximum joint efficiency, the welding temperature should not exceed the “softening temperature” of the base metal. But, to produce defect free welds favorable material flow in the weld nugget is necessary. The material flow and consolidation depend on the process temperature. Hence, for a given tool to produce defect free weld there is a need for minimum temperature. If the weld formation temperature is less than the base metal softening temperature, the weld can be made with 100% joint efficiency. In order to optimize the FSW parameter which gives defect free weld with lowest possible temperature, an instrumented programmable FSW machine is designed and developed. The machine is designed in such a way that welding parameters – rotation speed, traverse speed and plunging depth – can be continuously varied from the start to end of the weld between given two values. This reduces the number of experimental trials, material and time.
Based on the experimental results the following conclusions are derived.
1.The minimum diameter of the pin required for FSW depends on the base metal and tool material property for a given set of parameters. If the pin diameter is insufficient for a given set of welding parameters, it fails during plunging operation itself.
2.There is a minimum diameter of the shoulder for a given diameter of the pin which produces defect free weld. The ratio of pin to shoulder to produce a defect free weld is not a constant value. It changes with tool geometry and process parameters.
3.Increasing the area of contact between the tool and shoulder for a given set of parameters increases the heat input and results in increased weld nugget grain size.
4.Initial abutting interface of the base metal is eliminated at the leading edge of the tool. However, new surfaces are generated due to interaction with the tool and the newer surfaces are consolidated at the trailing edge of the tool. Importantly, the weld strength is controlled by the defects generated due the improper elimination of newly generated surfaces.
5.Optimal axial load is required to generate the required pressure to consolidate the transferred material at the trailing edge of the tool and should be equal to the flow stress of the material at the processing temperature. The optimal axial load is 8.1kN for a tool having 20mm diameter shoulder with 6mm diameter frustum shaped pin.
6.Only the material that approaches the tool at the leading edge on the advancing side is stirred and the remaining material is simply extruded around the tool. Further, the initial abutting interface is completely removed only when it is located in the stirring zone, otherwise the initial abutting interface is not eliminated. In the present study the interface is completely stirred when it is located on the advancing side of the tool between 0.5mm away from the centerline and edge of the tool.
7.The temperature and pressure at the tool–base metal interface is above the temperature and pressure required for seizure to occur for given tool material (H13) and base metal (7020-T6). Hence, it is clear that during FSW the base metal transfers on to the tool and interaction occurs between transferred layer on tool and base metal. The coefficient of friction between the given tool material and base metal in FSW condition is in the range of 1.2 – 1.4.
8.The minimum temperature requirement for FSW of 7020-T6 is 400oC and 6061-T6 is 430oC. However, 7020-T6 and 6061-T6 softens at lower temperatures than that of the minimum FSW temperature. 7020-T6 softens 30% in 7min at 250oC, 4min at 300oC, 2min at 350oC and 1min at 400oC. After softening 30%, there is 10% recovery in hardness and the hardness remains constant thereafter. Whereas 6061-T6 softens gradually up to 47% in 7min at 350oC and 400oC, below the temperature of 250oC for 7020-T6 and 350oC for 6061-T6 there is no softening observed in 7min.
9.The maximum joint efficiency of the 7020-T6 weld is 82% and 6061-T6 weld is 60%.
10. The reduction in joint efficiency is attributed to overaging of the material in the heat affected zone.
38
Youseffi, Mansour, Michael T. Martyn, and N. Showaiter. "Sintering and mechanical properties of prealloyed 6061 Al alloy with and without common lubricants and sintering aids." 2006. http://hdl.handle.net/10454/2731.
Full textAbstract:
NoPhysical and mechanical properties for prealloyed 6061 Al powder processed with and without additions of solid and/or liquid lubricants and sintering aids (Pb, Sn, Ag) are presented. For comparison, both vacuum and nitrogen sintering were carried out on as received (gas atomised) and degassed powder compacts pressed at 340 and 510 MPa. Vacuum degassing of the prealloyed powder provided better compressibility and thus higher green densities than those for the as received powder. Highest sintered densities of ~98-99% of theoretical were obtained for the prealloyed (and degassed) Al compacts by sintering under pure nitrogen with an addition of 0·6 wt-% paraffin wax as solid lubricant or 1·33 vol.-% liquid paraffin, or with a 0·12wt-%Pb addition as sintering aid and no lubricant. It was found that additions of solid lubricants such as lithium stearate and acrawax to both the premixed (elemental) and prealloyed powders provided reasonable green densities of ~94·5-95·5% TD, but had deleterious effect on sintered densities and microstructures, particularly under vacuum sintering. Other lubricants such as zinc stearate, stearic acid and liquid paraffin provided similar green densities, but higher sintered densities and less porous microstructures, particularly by sintering under pure nitrogen. The prealloyed compacts sintered under pure nitrogen consistently provided much higher sintered densities than elementally premixed compacts sintered under pure nitrogen or vacuum. It is therefore concluded that both lubricant type and sintering atmosphere will have a major effect on the sintered properties of the 6061 Al powder. Sintering under pure nitrogen resulted in higher sintered densities as compared with vacuum sintering for this grade of Al alloy. Tensile properties of the degassed and vacuum sintered (and T6 tempered) prealloyed powder compacts were higher than those of the equivalent alloy prepared by elemental mixing and comparable with those of the commercial (wrought) 6061 Al alloys.
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Sahu, Sushanta Kumar. "An appraisal of Characteristic Mechanical Properties of Aluminium 6061 alloy – Silicon Carbide (SiCp) Metal Matrix Composite (MMC) exposed to different thermal conditions." Thesis, 2009. http://ethesis.nitrkl.ac.in/1460/1/project-thesis-for-mohanty_sir.pdf.
Full textAbstract:
Aluminium 6061 alloys have been proposed for extensive use in automotive engine applications and there have been discrete cases of experimental implementation. In order to enhance the usability of this material, it has been investigated in composite forms with various ceramic
reinforcements. Viability of the different constituents depends on the compatibility of their physical and chemical properties. The service conditions are characterized by extreme stress and temperature conditions very close to failure. Hence thermal stresses play an important role in success of these materials.
The difference in the CTE of the alloy matrix and the ceramic reinforcement results in residual thermal stress build up. It may so cause plastic deformation of the matrix in the vicinity of the reinforcement in order to reduce the residual stresses. However, mismatch in thermal strain
values may lead to cracking of the matrix in this process.
In comparison with the matrix and reinforcement, the interface is rather a porous, non- crystalline portion. Therefore residual stresses are released at these sites with relative ease. When the particle fraction is high, interface availability is more; hence, failure of the MMC is due to formation and propagation of cracks at the interfaces. On the contrary, when particle fraction is less,
interface availability is poor; failure is predominantly due to particle cracking. In the present work, cylindrical Al 6061-SiCp MMCs are fabricated in the solid state
processing route. The sintering temperature and time of holding at the sintering temperature are varied. The samples are subjected to no thermal shock and thermal shocks at +80 ºC and -80 ºC in different batches. The compressive strengths are determined using an Instron (1195 ) adopting the ASTM E9 standard for hard metals. Fractured specimen are extensively analyzed with an SEM for
failure modes.
Assessment and evaluation on the basis of mechanical properties reveal that at relatively higher sintering temperature and for short term use, the thermal shock is not much damaging. For short- term use, the thermal shock at an elevated temperature is more damaging for samples sintered at lower temperature. For long-term use, the thermal shock due to a sub-ambient temperature is
more damaging when test specimen is sintered at relatively a lower temperature. The micrograph studies reveal that in general when the thermal shock is due to exposure to
an elevated temperature, inter-diffusion is high, resulting in strong bonding; hence, the dominating failure mode is cavity generation due to generation of discontinuities at the interface. And when the thermal shock is due to exposure to a sub-ambient temperature, the dominant failure mode is interfacial failure and/or matrix damage.
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Shi, Lei. "Zinc phosphating on 6061-T6 aluminum alloy." Thesis, 2000. http://hdl.handle.net/2429/10966.
Full textAbstract:
There is an urgent need to develop new non-chromating coating methods for the
corrosion protection of aluminum alloys, and this thesis reports studies to establish
optimal working conditions for forming zinc phosphate coatings on 6061-T6 aluminum
alloy. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS)
and corrosion tests were used to characterize the treated 6061-A1 surface, and to assess
the effects of different parameters in the coating bath, as well as different pre-treatments
and post-treatments.
The initial study investigated different working conditions for the zinc
phosphating, and this built on other studies from this laboratory. An initially considered
coating bath had 16.0 ml H3P04 (85%), 5.36 g ZnO and 0.5 g NaF per liter, and optimal
conditions for coating involved dipping the 6061-A1 samples into this bath at 60 °C for 6
min. But the addition of more fluoride was shown to be effective for increasing the zinc
phosphate coverage on the aluminum alloy; the optimal range of F" being from 400 ppm
to 600 ppm for these conditions.
Based on the working condition study, the effects of pre-treatments, posttreatments,
and associated procedures involved with the zinc phosphating of 6061-A1
alloy on the quality of the final coating were investigated. Comparisons were made
between acid etching and mechanical polishing in the pre-treatment stages, and the
mechanical polishing involved was done by either machine polishing or hand polishing.
New post-treatment procedures were investigated using methyltriethoxysilane. It results
in a considerable increase in the zinc phosphate coverage and coating thickness on the
aluminum surface. This gave a greatly improved corrosion resistance by the coating
compared with samples that did not have the silane post-treatment. A related silane
treatment can also be used at an intermediate stage in the zinc phosphating immersion.
In order to improve the final coating, Cu²⁺ and Ni²⁺ ions were studied as
accelerators. Cu(N0₃)₂ (0.002 wt%) and Ni(N0₃)₂ (0.0004 wt%) were separately
introduced to the basic phosphating baths containing H₃PO₄; ZnO and NaF, and each was
shown to not only increase the phosphating speed, but also to improve the corrosion
resistance and adhesion, insofar as the coating contained smaller crystalline grains and
increased coverage of zinc phosphate on the surface. Of these two accelerators, Ni²⁺
appeared especially effective at increasing the corrosion protection ability of the final
coating. Although NO³⁻ has some capabilities as an accelerator it was shown that its
effect was negligible in this context at the concentrations used.
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Srinivasan, Raghu. "Corrosion Studies Between Ceramics And 6061-T6 Aluminum." Thesis, 2005. http://hdl.handle.net/10125/10498.
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Huang, Ci Sin, and 黃信錡. "Causes of Corrosion Cracking in 6061 Aluminum Alloy Forgings." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/31525186697785752537.
Full textAbstract:
碩士長庚大學
機械工程學系
98
Aluminum alloys have been widely used in various applications, including being used in different kinds of corrosive environments. The objective of this study is to reduce the growth of stress corrosion cracking of AA6061 in chloride-containing environment via various thermomechanical processing. The experimental results indicate that rapid quenching after solution heat treatment may possibly retard the formation of precipitate-free zones (PFZ) along the grain boundaries, and subsequently reduce the growth of stress corrosion cracking. Overaging of the alloy may alter the distribution of the precipitates in the matrix and grain boundaries, and result in more severe growth of the intergranular cracking. As long as the AA6061 alloy is heat treated with T6 temper, the intergranular cracking cannot be successfully limited to the acceptance criterion, which is less than 200 µm deep underneath the sample surface. When the samples are forged to different degrees at room temperature prior to aging heat treatment, the characteristic of cracking becomes pitting instead of intergranular, and the penetrating depths of cracking are always significantly lower than 200 µm. It has been concluded that the T8 temper with various degrees of cold work can successfully retard the growth of stress corrosion cracking of AA6061 in the chloride-containing corrosive solution.
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Hu, S. H., and 胡少華. "An Investigation of Backward Flowforming for Aluminum Alloy 6061." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/66462380119311666304.
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莊文煌. "Weldability Studies of Different Aluminum Alloys 6061 and 7075." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/25341711101239924436.
Full textAbstract:
碩士國立交通大學
機械工程研究所
85
Aluminum 6061 and 7075 have high strength of weight ratio and good corrosion resistance but they are poor in weldability, 7075 especially. The major problems are distortion, porosity, hot cracking and HAZ strength reduction. This research was to explore the weldability of 6061 and 7075 precipitated hardening aluminum alloys under Gas Metal Arc (GMA) welding process, and filler metals ER4043 and ER5356 were used. A series of experiments including pulsed welding current, post weld heat treatment, micro hardness testing, tensile testing, bending test, optical microscope, SEM and EPMA were used to investigate the relationship between mechanical properties and microstructure. The experimental results showed that hot cracking canbe reduced in 7075 aluminum alloy welds made with suitable preheat. The proper post weld heat treatment can effectively increae the strength in fusion zone and HAZ. Precipitation in grain boundary and grain interior can cause hot cracking in 7075 aluminum alloy weld. The porosity content of the pulsed-current weld is in general found to be comparatively lower than that of the continuous current weld. The increase in zinc pickup in fusion zone can enhances the ultimate tensile strnegth of the weldment.
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Chen, Sin-Yu, and 陳心畬. "Study of TiC Powder Cladding on 6061 Aluminum Alloy." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/96240590728871874332.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
100
In this thesis, the TiC particles were clad on 6061 alminum alloy by the gas tungsten arc welding(GTAW) method to investigate improvement of wear resistance. Besides, the factors which influenced hardness and wear performance of the clad layers were determined by the Taguchi parameter design method. The cladding-process parameters for improving the hardness and wear resistance of 6061 aluminum alloy surface were changed according to Taguchi parameter design method. In addition, trial and error method was applied for the cladding processes on 6061 aluminum alloy and a surface-covered aluminum method was developed. According to the experimental results by Taguchi method, which showed that the hardness of the clad layers were influenced the most by mixed powders, aluminum content, and travelling speed ; the wear characteristics were determined by mixed powders, welding current and travelling speed most. The characteristics of the added particles presented large effects on the hardness and abrasion resistance of the clad layers. Additionally, input heat determined by the welding current and travelling speed affected the microstructure of the clad layers.
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Lung, Yung-Feng, and 龍永豐. "The Trimming Behavior of an Early-Aged 6061 Aluminum Alloy." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/97729302862539535479.
Full textAbstract:
碩士逢甲大學
材料與製造工程所
94
The thesis, “The Trimming Behavior of an Early-Aged 6061 Aluminum Alloy” would often help in properly using industrial stamping machines as the main process to manufacture certain components. Getting the most reliable result from the stamping process strongly relies on the material condition. Aluminum alloy 6061 is heat treatable and can be age hardened to adjust the material properties by applying different parameters in the aging treatment. The most efficient way to stamp a piece out of a plate of raw material is to use soft material since it requires the consumption of less working energy compared to hard materials. However, the softest material is not always the best condition for the operation. For example, relatively low tensile strength of stamped material results a thicker fracture surface, which is not desirable to the function. Also, softer material gives a bigger die roll. The experiment was designed from two directions : first, to evaluate the stamping result, and second, to compare it with the change of material properties in each condition according to hardness tests, impact tests and tensile tests. Furthermore, an analysis in the change of material microstructure and dislocation behavior was carried out by HRTEM, SEM, OM and DSC as the assistance in finding the connection with the change of material properties in each step. The results of the study indicate that the most suitable conditions of the aged 6061 aluminum alloy (applied aging treatment under 160℃) for the stamping operation is in the aged lead time between 10 minutes to 35 minutes. The burnished surface in the operation under this condition was nearly 45% of the material cross section height. The burnished surface in material cross section height in the operation using as fabricated material was just 34%, and it requires the post-heat treatment to enhance the strength of material properties, however, that would seriously cause the problem of deformation in the well stamped components to its dimensions. Two of key material properties dominate the working result for the existence of burnished surface from the study, that is toughness and tensile strength. The triming behavior turns less effective when the toughness or tensile strength becomes too high. The observation of the microstructure on the broken surface of the impact specimens indicated an ductile-brittle mixed fracture was found in the specimens with aged lead time of 40-minute-long and extended.
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Lin, He-I., and 林和儀. "Development of Dual-beam Hybrid Welding Aluminum Alloy 6061 Process." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/39066517661959607069.
Full textAbstract:
碩士國立高雄第一科技大學
機械與自動化工程研究所
99
CO2 laser welding of aluminum alloy is easily formation of holes, how to effectively improve the welding of aluminum alloys produced pores is extremely important. The MIG hybrid welding can be generated heat in order to improve the material''s surface structure which increase the absorption rate of materials to reduce the generation pores and prevent the emergence of the weld cracking turtle. Hybrid welding of CO2 laser and MIG, many of scholars had already proposed research experiments, and find ways to overcome the defects after welding, which the most difficult is overcome the shortcomings of residual pores. This study is using three shield gases, so that results shown to effectively reduce the formation of pores. Development of Dual-beam Hybrid Welding Aluminum Alloy 6061 Process, using variety of welding parameter combinations,and consider to explore the genesis and amount of porosity, then application Taguchi principal component analysis and fuzzy theory analysis for weld the tensile strength, weld micro-hardness, porosity degree,bending strength and other quality characteristics of aluminum alloy 6061, inferences Dual-beam Hybrid Welding Aluminum Alloy 6061 Process,and development of multi-objective optimization hybrid welding parameter combinations, in order to enhance various properties significantly.
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Chang, Yuan-feng, and 張源峰. "CO2 Laser-MIG Arc Hybrid Welding of Aluminum Alloy 6061." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/70673189222840999376.
Full textAbstract:
碩士國立高雄第一科技大學
機械與自動化工程所
93
The combination of laser and MIG arc is internationally becoming a potentially useful technique after being researched for years abroad. The hybrid welding process has been demonstrated to offer the advantages of enabling to increase depth penetration ratio, welding speed, and decrease the susceptibility of hot cracking etc. However, this technique is still in its infancy in the domestic industrial applications. If the hybrid welding was successfully developed, it is expected to reduce the post-processing cost, enhance the weldmental quality, and eventually the competitiveness if introduced to Taiwan manufacturing-related industries. In this paper, the welding of 6061 aluminum alloy was carried out using the combined sources of the CO2 laser beam and the MIG arc. Due to that the CO2 laser-MIG arc hybrid welding has been operated using the trial-and-error method, and the process was essentially not unreliable. Therefore, this research aims to not only develop the technology of CO2 Laser-MIG arc hybrid welding of aluminum alloy 6061-T6, but also to optimize multiple performance characteristics of hybrid welding using Taguchi methods coupled with principal component analysis (PCA). The multiple characteristics investigated include tensile strength, bending strength, and micro-hardness etc. According to experimental results, the optimal process conditions for the hybrid welding process can be determined as A2 (filler material: aluminum alloy 5356), B3 (laser power: 1450W), C3 (MIG current: 155A), D2 (welding speed: 550mm/min), E3 (gap size: 0.3mm), F1 (laser assist gas flow: 30kg/cm2), G2 (MIG assist gas flow: 26kg/cm2), and H1 (wire extension length: 12mm), which improve tensile strength, elongation ratio, porosity ratio, and bending strength for the weldments quality. In addition, the analysis of variance (ANOVA) shows that the test is highly reliable in the hybrid welding experiment due to error 4.0068%.
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Wang, Wei-Lun, and 王偉倫. "CO2 Laser-TIG Arc Hybrid Welding of Aluminum Alloy 6061." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/30700517854813089647.
Full textAbstract:
碩士國立高雄第一科技大學
機械與自動化工程所
93
Aluminum alloy is used broadly because it has many advantages, such as: light specific gravity, nice plasticity, processing easily, no low temperature brittleness and capable of being corrosion. Due to the reflection of CO2 laser goes up to 97%, the first question is how to raise the absorption rate of material effectively when CO2 laser welds aluminum alloy. Hybrid welding can improve the exterior construction of the material, increase the absorption rate of material, reduce the forming of pore and prevent the crack of the welding channel by the heat source of TIG. In the beginning, the research takes advantage of the change of welding velocity, and then conduct a BOP test to observe the relation of laser, TIG and CO2 laser go with the penetration and welding velocity of TIG arc laser. At last, use the figures of both current-time and voltage-time to calculate the power of TIG to compare the relativity of the laser. The research especially focuses on improving the problems of pore and crack after hybrid CO2 laser goes with TIG welding. Use different kinds of methods of welding parameter combination to probe into the production and numbers of pore. The study presents the application Taguchi methods coupled with Principal component analysis（PCA） in the process of optimization of the hybrid CO2 laser-TIG welding aluminum alloy 6061. A set of optimal process conditions for producing the tensile strength, bending strength, micro-hardness and pore percentage developed.
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Bandar, Alexander Raymond. "Modeling microstructure evolution in the dead-metal zone of indirectly extruded 6061 aluminum /." Diss., 2005. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3167046.
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