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Статті в журналах з теми "Microstructural gradient":
1
Chen, Yan Hong, T. Li, and Jan Ma. "Electrophoretic Deposition of Functionally Graded Monomorph." Key Engineering Materials 314 (July 2006): 89–94. http://dx.doi.org/10.4028/www.scientific.net/kem.314.89.
Анотація:
In the present work, investigation of the functional property of piezoelectric graded monomorph actuator systems is presented. The functional graded actuators were fabricated by electrophoretic deposition (EPD) using pure PZT and doped PZT materials. Actuators developed have shown gradual gradient variation in microstructure. It is noted that trend in microstructural gradient does not represent similar trend in piezoelectric property gradient. The displacement of microstructural graded and both piezoelectric and microstructural graded actuators were measured. The results show that the gradient distribution of the piezoelectric properties is important to improve the electromechanical performance of the actuator.
2
Schmidt, Christopher David, Hans-Jürgen Christ, and Axel Von Hehl. "Hydrogen as a Temporary Alloying Element for Establishing Specific Microstructural Gradients in Ti-6Al-4V." Metals 12, no. 8 (July 28, 2022): 1267. http://dx.doi.org/10.3390/met12081267.
Анотація:
Parts of vehicles, such as landing gear components of aircrafts, are subject to growing demands in terms of sustainability via lightweight design and durability. To fulfill these requirements, the development of thermochemical processes is auspicious. Titanium alloys allow a heat treatment in hydrogen-containing atmosphere for temporary hydrogen alloying, often called thermohydrogen treatment (THT). The investigation presented intends to realize a local microstructure modification of Ti-6Al-4V by means of THT. The study aims to use hydrogen (H) as a promoter for changing the local distribution and morphology of strengthening precipitates during THT as well as the local grain size (microstructural gradient). Both shall improve the fatigue properties of the material after hydrogen degassing. To derive suitable thermohydrogen treatment process parameters, the resulting fatigue crack propagation resistance and fracture toughness after different solution heat treatments are determined experimentally and compared to each other. Moreover, various graded microstructures are evaluated after hydrogen uptake (hydrogenation) and hydrogen degassing (dehydrogenation) using numerically simulated hydrogen concentration profiles, observed hardness curves, metallographically determined microstructure gradients and the corresponding results of the phase analysis by means of X-ray diffraction. The study shows that hydrogenation at 500 °C and dehydrogenation at 750 °C enables the generation of a promising microstructural gradient.
3
Rabin, B. H., and I. Shiota. "Functionally Gradient Materials." MRS Bulletin 20, no. 1 (January 1995): 14–18. http://dx.doi.org/10.1557/s0883769400048855.
Анотація:
This issue of the MRS Bulletin provides an up-to-date look at ongoing research activities within the field of functionally gradient materials (FGM). The term FGM, now widely used by the materials community, originated in Japan in the late 1980s as a description for a class of engineering materials exhibiting spatially inhomogeneous microstructures and properties. Of course, gradient materials are not something new. It must be recognized that humans have extensively utilized materials containing microstructural gradients (either those found in nature or those created through processing) since the earliest days of craftsmanship and engineering construction. Indeed, there are examples of graded materials developed long ago, such as case-hardened steel, which are still in common use today. Contemporary examples of these materials serve in technologically significant applications, as, for example, in thermal-barrier coatings for gas turbines. Nevertheless, what is new and exciting about FGMs is the realization that gradients can be designed at the microstructural level to tailor a material for the specific functional and performance requirements of an intended application. In addition, recent advances in processing are opening the possibility for the extension of the gradient materials concept to new materials systems and engineering problems.The recent resurgence of interest in gradient materials has been driven by the need for improved materials, capable of meeting the demanding performance requirements established by emerging technologies such as the aerospace plane, ceramic engines, and nuclear fusion.
4
Schmidt, Christopher David, Vitali Macin, Peter Schmidt, and Hans-Jürgen Christ. "Generation of Microstructural Gradients for Improved Mechanical Properties via Thermo-Hydrogen Treatment of the Metastable Beta Titanium Alloys Beta CTM and Ti 10V-2Fe-3Al." MATEC Web of Conferences 321 (2020): 12017. http://dx.doi.org/10.1051/matecconf/202032112017.
Анотація:
Structural components must be lightweight and produced resource-saving while still fulfil the increasing durability and reliability requirements. One approach to fulfil these requests is a temporary hydrogen charging of Ti-alloys, which generates lattice distortion and hydrides. The volume difference between hydride precipitates and the alloy matrix results in localized plastic deformation. This triggers recrystallization and enables a finer microstructure as attainable by a conventional heat treatment. The study aims at an elaboration of a thermo-hydrogen treatment that establishes a change in grain size and/or an alteration in distribution and morphology of strengthening secondary α precipitates as a function of the distance to surface (microstructural gradient). The gradient is based on a gradient of the hydride volume fraction. Generally, THT design requires kinetic (temperature dependency of the hydrogen diffusion coefficient DH) in addition to thermodynamic (H/β-Ti-alloy interaction) data, which has been obtained for Ti 3Al-8V-6Cr-4Mo-4Zr and Ti 10V-2Fe-3Al. Subsequent to a solution treatment the variation of hydrogenation time and temperature is operated to establish comparably slight microstructural gradients on these materials. For further investigations it is concluded that materials with less alloying elements ((α+β)-Ti-alloys (e.g.,Ti 6Al-4V)) than these β-Ti-alloys can satisfy the requirements to generate steeper microstructural gradients even better.
5
Ueno, Kouki, Akira Sato, and Hiroyuki Sato. "Formation of Microstructural Gradient of A2017 by RBT at Ambient Temperature." Materials Science Forum 794-796 (June 2014): 1233–38. http://dx.doi.org/10.4028/www.scientific.net/msf.794-796.1233.
Анотація:
Distribution of microstructure and hardness by RBT (Rotary Bending and Tensile) loading at ambient temperature is presented. Grain size is one of the important parameters of microstructures of alloys, and affects mechanical characteristics depending on deformation conditions. At higher temperatures, coarsening of grain size improves creep strength, while the finer improve tensile strength at ambient temperature. Grain size shows opposite effect on strength of alloys depending on temperatures and not always possible to improve strength both at ambient and high temperatures. Authors have attempted microstructural control by formation of distribution of plastic strain prior to heat treatment of aluminum alloys to obtain well-balanced strength both at high and ambient temperatures. In this report, distribution of grain size and hardness in 2017 aluminum by RBT loading are presented, and compared with results in 1070 reported previously. RBT loading equipment is designed for combined loading by rotary bending and static tensile loading to distribute plastic strain. In 2017 alloy, obtained microstructure after suitable heat treatment show distribution of hardness, while grain size show homogeneous distribution. The distributions, however, are different from that in 1070 alloy.
6
Pei, Wanrong, Tongde Wu, Zhiwen Wang, Yunlei Jiang, Chuanping Zhou, Rougang Zhou, and Yongping Gong. "Reflection of Elastic Waves in Dipolar Gradient Half-Space under the Control of External Magnetic Field." Applied Sciences 14, no. 1 (December 31, 2023): 376. http://dx.doi.org/10.3390/app14010376.
Анотація:
This paper investigated the reflection of plane waves at the interface of dipolar gradient elastic solids under the control of an external magnetic field. This study focused on the increasing influence of the microstructural effect as the incident wavelength approaches the characteristic length of the microstructure or at higher frequencies. Initially, the dispersion equation for the propagation of elastic waves was derived from the dipole strain gradient theory and Maxwell’s electromagnetic theory. Subsequently, the amplitude ratios of various reflected waves to incident P-waves and incident SV-waves were calculated based on the interface conditions. Finally, the numerical results were used to discuss the impact of the external magnetic field and microstructural characteristic length on the propagation of the reflected wave. It was observed that the microstructural effect generated new wave modes and introduced dispersion characteristics into the elastic waves. Conversely, the external magnetic field primarily influences the amplitude of the elastic wave propagation via the Lorentz force without creating new wave modes or affecting the dispersion properties of the elastic wave in the dipolar gradient elastic solid.
7
Seo, Seongji, and Jiyong Park. "Annealing Heat Treatment for Homogenizing the Microstructure and Mechanical Properties of Electron-Beam-Welded Thick Plate of Ti-6Al-4V Alloy." Materials 16, no. 23 (November 29, 2023): 7423. http://dx.doi.org/10.3390/ma16237423.
Анотація:
In the application of Ti-6Al-4V to aerospace structural components, when welding thick plates similar of the thickness of the components, microstructure and hardness gradients emerge between the base material (BM) and the joint. This leads to the issue of significant stress concentration in the BM under tensile stress. To address this problem through post-welding heat treatment, this study conducted heat treatments at temperatures both below (mill annealing, MA) and above the beta-transus temperature (beta annealing, BA) on electron-beam weldments of 18 mm thickness Ti-6Al-4V plates. Subsequently, microstructures and hardness were analyzed at different depths from the upper surface and areas (fusion zone (FZ), heat-affected zone (HAZ), and BM), and tensile properties were measured at various depths. The results indicated that α′ observed in FZ and HAZ was resolved through both MA and BA. Particularly after BA, the microstructural gradient that persisted even after MA completely disappeared, resulting in the homogenization of widmanstätten α + β. Consequently, after BA, the hardness gradient in each zone also disappeared, and the tensile strength was higher than in just-welded and MA heat-treated plates.
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Liu, Mulin, Naoki Takata, Asuka Suzuki, and Makoto Kobashi. "Effect of Heat Treatment on Gradient Microstructure of AlSi10Mg Lattice Structure Manufactured by Laser Powder Bed Fusion." Materials 13, no. 11 (May 29, 2020): 2487. http://dx.doi.org/10.3390/ma13112487.
Анотація:
The present study addressed the effect of heat treatment process on microstructure of an AlSi10Mg lattice structure with a body-centered cubic unit cell manufactured via laser powder bed fusion (LPBF). The as-manufactured lattice specimen exhibited a unique cellular structure composing of primary α-Al phases bounded by α-Al/Si eutectic microstructure. A gradient microstructure (continuous microstructural changes) was found in the node and strut portions composed of the lattice specimen. The microstructure appears more equiaxed and coarser with approaching the bottom surface of both portions. The continuous microstructural changes contributed to a variation in hardness measured at different locations in the as-manufactured lattice specimen. Si particles finely precipitate in the primary α-Al phases, and eutectic Si particle coarsening occurs at an elevated temperature of 300 °C. The microstructural coarsening is more pronounced at a higher temperature. A number of significantly coarsened Si particles and a stable Fe-containing intermetallic phase (β-AlFeSi) were observed at all locations in 530 °C solution-treated specimen. The homogenous microstructure results in a constant hardness value independent of the location in the lattice specimen. These results provide new insights to control the compressive properties of the AlSi10Mg lattice structure manufactured via LPBF by subsequent heat treatment processes.
9
Liu, Yao, and Songlin Cai. "Gradients of Strain to Increase Strength and Ductility of Magnesium Alloys." Metals 9, no. 10 (September 22, 2019): 1028. http://dx.doi.org/10.3390/met9101028.
Анотація:
A strain gradient was produced in an AZ31B magnesium alloy through a plastic deformation of pure torsion at a torsional speed of π/2 per second. Compared with the base material and with the alloy processed by conventional severe plastic deformation, the magnesium alloy provided with a strain gradient possesses high strength preserving its ductility. Microstructural observations show that strain gradient induces the formation of an inhomogeneous microstructure characterized by statistically stored dislocation (SSD) density gradient and geometrically necessary dislocation (GND). GNDs and dislocation density gradient provide extra strain hardening property, which contributes to the improvement of ductility. The combination of SSD density gradient and GND can simultaneously improve the strength and ductility of magnesium alloy.
10
Mishnaevsky, Leon. "Computational Analysis of the Effects of Microstructures on Damage and Fracture in Heterogeneous Materials." Key Engineering Materials 306-308 (March 2006): 489–94. http://dx.doi.org/10.4028/www.scientific.net/kem.306-308.489.
Анотація:
3D FE (finite element) simulations of the deformation and damage evolution of particle reinforced composites are carried out for different microstructures of the composites. Several new methods and programs for the automatic reconstruction of 3D microstructures of composites on the basis of the geometrical description of microstructures as well as on the basis of the voxel array data have been developed and tested. Different methods of reconstruction and generation of finite element models of 3D microstructures of composite materials (geometry-based and voxel array based) are discussed and compared. It was shown that FE analyses of the elasto-plastic deformation and damage of composite materials using the microstructural models of materials generated with these methods yield very close results. Numerical testing of composites with random, regular, clustered and gradient arrangements of spherical particles is carried out. The fraction of failed particles and the tensile stress-strain curves were determined numerically for each of the microstructures. It was found that the rate of damage growth as well as the critical applied strain, at which the damage growth in particles begins, depend on the particle arrangement, and increase in the following order: gradient < random < regular < clustered microstructure.
Дисертації з теми "Microstructural gradient":
1
Guevenoux, Camille. "Réparation de pièces métalliques par Directed Energy Deposition : gradient microstructural, comportement mécanique et tenue en fatigue." Thesis, Institut polytechnique de Paris, 2021. http://www.theses.fr/2021IPPAX006.
Анотація:
Le Directed Energy Deposition (DED) est un procédé de fabrication additive utilisant une buse constituée d’un faisceau laser et d’un jet de poudre coaxiaux. Le laser crée un bain liquide dans lequel la poudre est projetée, elle fond puis se solidifie formant un cordon de matière lorsque la buse se déplace. Ce procédé présente en particulier un fort potentiel pour réparer des pièces métalliques à haute valeur ajoutée. Néanmoins, le faible diamètre et les mouvements rapides du faisceau laser entraînent des gradients thermiques et des vitesses de refroidissement élevés et cette évolution thermique spécifique est responsable de la formation de microstructures différentes de celles des composants traditionnels mis en forme par forge ou fonderie. Ainsi, les composants réparés présentent une interface qui sépare le matériau de base (souvent forgé) et la région reconstruite par DED. Ce gradient microstructural conduit à un gradient de propriété et donc à des phénomènes de localisation qui affectent la durée de vie des composants réparés. Cette thèse propose une méthode de caractérisation de la zone d'interface des composants réparés. Un outil semi-analytique de modélisation des champs de température pendant le procédé de rechargement a été mis au point pour concevoir des éprouvettes représentatives géométriquement et thermiquement de la réparation sur la pièce réelle. Le gradient de microstructure à travers l'interface est d'abord caractérisé par imagerie MEB et par analyse EBSD. Des éprouvettes de traction sont ensuite prélevées à l'interface et sollicitées lors d’essais conduits sous MEB. La déformation est suivie à l'échelle micrométrique par corrélation d'images, ce qui permet d'étudier les phénomènes de localisation. Par la suite, ces cartes expérimentales sont utilisées pour identifier le comportement local du matériau dans la région de l’interface, en minimisant l’erreur entre les champs de déformation expérimental et numérique. Le gradient de propriété ainsi déterminé permet de calculer la répartition de contraintes dans des éprouvettes soumises à des essais de fatigue. La limite d'endurance des structures réparées est ensuite calculée à partir des résultats expérimentaux d'une campagne de fatigue et comparée à celle de la pièce d'origine pour déterminer l'abattement causé par le rechargementDirected Energy Deposition (DED) process is a powder-jet additive manufacturing process involving a nozzle composed of coaxial laser beam and powder stream. The laser generates a melt pool in which the powder is projected, it melts and then solidifies creating a deposit as the nozzle moves. However, this process is particularly appealing to repair valuable metallic components. The small spot size and fast motions of the laser causes strong thermal gradient and important cooling rates and this specific thermal evolution is responsible for the formation of microstructures different from traditional processes like forge or foundry. Consequently, the repaired components exhibits an interface between the base material (generally wrought) and the region reconstructed with DED. This microstructural gradient leads to a mechanical gradient and therefore to localization phenomena which can affect the lifetime of repaired components. This thesis proposes a method to characterize the interface region of repaired components. A semi-analytic tool has been developed to model the thermal evolution during the repair process in order to design representative specimens, in terms of geometry but also in terms of thermal history. The microstructural gradient through the interface is first characterized with a SEM and EBSD analyses. Tensile specimen are then taken in the interface region and loaded during SEM in-situ tests. The strain is followed at the micrometric scale with Digital Image Correlation, what provides the information regarding localization phenomena. Those experimental data are then injected into a numerical method to identify the local parameters of the mechanical behavior by minimizing the error between the experimental and numerical fields. Using this mechanical gradient, the stress in fatigue specimens is derived. A fatigue limit is then derived from the experimental results of the fatigue tests and it is compared to the endurance of the original part to estimate the reduction of resistance caused by the repair
2
Hasan, Md Nazmul. "Microstructure and mechanical properties of a CrMnFeCoNi high-entropy alloy with gradient structures." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23036.
Анотація:
High-entropy alloys (HEAs) that demonstrate excellent mechanical properties over steel-based alloys are not exempt from the common dilemma of strength–ductility trade-off, which limits their potential applications. One way to improve the property of CrMnFeCoNi HEA is by using the rotationally accelerated shot peening technique to introduce a gradient structure. Two gradient profiles—a thin gradient layer with an undeformed core and a fully deformed structure—are introduced by adjusting the processing parameters. The effects of these gradient profiles on mechanical properties and microstructural evolution at various loading conditions and temperatures are systematically explored. In this thesis, various mechanical tests are performed to investigate the effect of the gradient structure on mechanical properties such as tensile properties at room and cryogenic temperatures, compression at different strain rates and dynamic compression at high strain rates. Material characterisations are performed using various electron microscopic techniques to build a structure–property relationship and investigate microstructural evolution.
3
Appiah, Kwadwo Ampofo. "Microstructural and microanalytical characterization of laminated (C-SiC) matrix composites fabricated by forced-flow thermal-gradient chemical vapor infiltration (FCVI)." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/14910.
4
Liu, Meishuai. "Study on microstructural and crystallogarphic characteristics of phase transformation induced by ECP in annealed Cu-40%Zn alloy." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0210.
Анотація:
Ce travail porte sur les caractéristiques microstructurales et cristallographiques des alliages Cu-40%Zn traités par Electric Current Pulse (ECP). La relation d'orientation (RO) de transformation de phase et sa corrélation avec les défauts cristallins ont été étudiés. Les mécanismes de formation des défauts cristallins dans la phase mère et des sous-structures dans les précipités β induit par L'ECP ont également été étudiés. La transformation de la phase α en β peut être induite par un traitement ECP avec formation de précipités fins β pouvant persister à température ambiante. Avec l'augmentation de la densité de courant électrique, la quantité de précipités et les sites de formation augmentent des joints de grains α à l'intérieur des grains. Les précipités β suivent différentes RO en fonction du site de formation. Les joints de grains β sont en RO Kurdjumov-Sachs (KS); tandis que les β intragranulaires sont en Nishiyama-Wasserman (NW). Dans les premiers sites, on observe des dislocations {111}α/<11̅0>α, alors que dans les seconds, les fautes d’empilements {111}α/<112̅>α sont présentes. Les analyses de déformation de transformation ont révélé que, en RO KS, la déformation maximale du réseau requise est un cisaillement sur le système {111}α/<112̅>α, tandis qu'en NW, la déformation maximale correspond à un cisaillement sur le système {111}α/<112̅>α. Ainsi, les dislocations {111}α/<11̅0>α existants le long des joints de grains α fournissent la précontrainte requise par la transformation KS, alors que les fautes d'empilement {111}α/<112̅>α entourées par les dislocations partielles {111}α/<112̅>α offrent une précontrainte facilitant la transformation NW. Différents types de défauts cristallins sont formés dans la matrice α par les traitements ECP en fonction de la densité de courant. À faible densité, une grande quantité de fautes d'empilement {111}α/<112̅>α, puis des nano-mâcles sont produites dans la matrice α. A haute densité, des réseaux de dislocations sont formés à proximité des précipités β composés de dislocations coins parfaites {111}α/<11̅0>α et des dislocations de Frank. La différence de volume entre le phases α et β analysée avec la déformation de transformation révèle que cette dernière nécessite une dilatation dans la direction [11̅0]α et une contraction dans la direction [111]α. La première entraîne l’apparition de dislocations coins {111}α/<11̅0>α devant les larges faces {31̅1}α et la dernière induit la formation des dislocations de Frank devant les larges faces {121}α. Ainsi, des réseaux de dislocations se forment le long des bords des grandes faces des précipités β où les deux types de dislocations se rencontrent. De plus, les précipités β contiennent deux types d’agrégats atomiques de taille nanométrique de structure n en RO Burgers et de structure ω en RO Blackburn avec la matrice β. Ils ont été formés par un déplacement atomique en deux étapes. Pour la structure n, la première étape est le brassage atomique de chaque second plan {110}β dans la direction <11̅0>β et la seconde consiste en un changement de structure principalement par un cisaillement selon {11̅2}β /<1̅11>β. Pour la structure ω, le premier est un mélange atomique sur chaque deuxième et troisième plan {112̅}β dans les directions ±[111]β, puis des déformations normales dans trois directions perpendiculaires (<111>β, <112̅>β et <11̅0>β). L’apparence concomitante des deux structures réside dans le fait que l’augmentation de volume accompagnant la formation de n peut être annulée par la diminution de volume accompagnant la distorsion ω, ce qui minimise l’énergie de déformation de transformation. Ce travail fournit des informations fondamentales sur les alliages Cu-40%Zn pour interpréter l’impact des défauts sur les relations d'orientation de transformations en phase solide, sur la formation de divers types de défauts induits par la transformation de phase ultra-rapide ainsi que sur les mécanismes de formation des sous-structures des phases produitesA thorough investigation has been conducted on the microstructural and crystallographic features of Electric Current Pulse (ECP) treated Cu-40%Zn alloys. The phase transformation orientation relationship (OR) and its correlation with crystal defects have been studied and the formation mechanisms of ECP induced crystal defects in the parent phase and the sub-structures in the β precipitates were also analyzed. The α to β heating phase transformation can be induced by ECP treatment with the formation of fine β precipitates that can be remained to the room temperature. With the increase of the electric current density, the amount of precipitates is increased and the formation sites increase from α grain boundaries to grain interiors. The β precipitates follow different ORs depending on the formation site. The grain boundary β phase obeys the Kurdjumov-Sachs (K-S) OR; whereas the intragranular β respects the Nishiyama-Wasserman (N-W) OR. In the former sites, the {111}α /<11̅0>α dislocations are observed, whereas in the latter, the {111}α/<112̅>α stacking faults are found. Transformation strain analyses revealed that under the K-S OR the maximum lattice deformation required is a shear on the {111}α /<11̅0>α slip system, whereas under the N-W OR the maximum deformation is a shear on the {111}α /<112̅>α system. Thus the existing {111}α /<11̅0>α dislocations along the α grain boundaries provide pre-strain required by the transformation via the K-S path, whereas the {111}α /<112̅>α stacking faultsboarded by {111}α /<112̅>α partial dislocations offer pre-strain facilitating the transformation via the N-W path. Different types of crystal defects are formed in the α matrix by the ECP treatments depending on the current density. At low density, large amount of {111}α /<112̅>α stacking faults and then nano twins are produced in the α matrix. At high density, dislocation nets are formed near the β precipitates that are composed of edge typed {111}α /< 11̅0 >α perfect dislocations and the Frank typed dislocations. The volume misfit between the α and the β phase analyzed with transformation deformation reveals that the transformation from α to β requires an expansion along [11̅0]α direction and a contraction along [111]α direction. The former results in the appearance of the {111}α /<11̅0>α edge typed dislocation arrays in front of the {31̅1}α broad faces and the latter induces the formation of the Frank typed dislocations in front of the {121}α broad faces. Thus, dislocation nets formed along the edges of the broad faces of the β precipitates where the two kinds of dislocations meet. Furthermore, the β precipitates contain two kinds of nano-sized and diffuse atomic clusters with the structure obeying the Burgers OR and with the ω structure obeying the Blackburn OR with the β matrix. They were each formed through a two-stepped atomic displacement. For the structure, the first step is the atomic shuffle of each second {110}β plane in the <11̅0>βdirection and the second is a structure change mainly by a shear on the {11̅2}β /<1̅11>β. For the ω structure, the first is an atomic shuffle on each second and third {112̅}β plane in the ±[111]β directions and then normal strains in three mutually perpendicular directions (<111>β, <112̅>β and <11̅0>β). The concomitant appearance of the two structures lies in the fact that the volume increase accompanying the formation can be canceled by the volume decrease accompanying the ω distortion, which minimizing the transformation strain energy. The results of this work provide fundamental information on the Cu-40%Zn alloys for interpreting the impact of the crystal defects on the solid phase transformation ORs, on the formation of various types of crystal defects induced by the ultra-rapid phase transformation and on the formation mechanisms of sub structures in the product phase
5
Thomas, Jonova. "Microstructural Phase Evolution In Laser Deposited Compositionally Graded Titanium Chromium Alloys." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849610/.
Анотація:
A compositionally graded Ti-xCr (10≤x≤30 wt%) alloy has been fabricated using Laser Engineered Net Shaping (LENSTM) to study the microstructural phase evolution along a compositional gradient in both as-deposited and heat treated conditions (1000°C followed by furnace cooling or air cooling). The alloys were characterized by SEM BSE imaging, XRD, EBSD, TEM and micro-hardness measurements to determine processing-structure-property relations. For the as-deposited alloy, α-Ti, β-Ti, and TiCr2 (C15 Laves) phases exist in varying phase fractions, which were influential in determining hardness values. With the furnace cooled alloy, there was more homogeneous nucleation of α phase throughout the sample with a larger phase fraction of TiCr2 resulting in increased hardness values. When compared to the air cooled alloy, there was absence of wide scale nucleation of α phase and formation of ω phase within the β phase due to the quicker cooling from elevated temperature. At lower concentrations of Cr, the kinetics resulted in a diffusionless phase transformation of ω phase with increased hardness and a lower phase fraction of TiCr2. In contrast at higher Cr concentrations, α phase separation reaction occurs where the β phase is spinodally decomposed to Cr solute-lean β1 and solute-rich β2 resulting in reduced hardness.
6
Müller, Guillaume. "Conception, élaboration et caractérisation de matériaux de composition et de microstructure innovants pour les micro-piles à combustible à oxyde solide." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00833281.
Анотація:
Les micro-piles à combustible à oxyde solide (micro-SOFC) apparaissent comme des sources d'énergie miniatures attractives et constituent une réelle rupture technologique permettant une solution alternative aux accumulateurs Li-ion actuels. Dans ce contexte, ce travail concerne la synthèse, la caractérisation structurale, microstructurale et électrochimique de films minces denses et poreux de composition et de structure variées : LSCF-CGO, Ni(O)-CGO et CGO. Ces matériaux ont été intégrés comme cathode, anode et électrolyte respectivement dans un dispositif type micro-SOFC fonctionnant vers 400-600°C à partir de H2 comme carburant. L'architecture de la cellule et son procédé de synthèse diffèrent de ceux proposés dans la littérature. En effet, des gradients de porosité et de composition ont été réalisés aux électrodes de manière à limiter les phénomènes de polarisation d'activation et de concentration. De plus, le choix du procédé de synthèse, sol-gel couplé à la méthode de trempage-retrait pour la mise en forme des matériaux, a été guidé par des critères économiques et de facilité de mise en œuvre. Pour la synthèse des films minces denses d'électrolyte (CGO), une autre méthode de synthèse (ALD) a également été utilisée. Dans ce travail, nous avons étudié plus particulièrement les relations qu'il existe entre les propriétés structurale, microstructurale et électrique des films minces poreux d'électrodes, dans les conditions de synthèse et de fonctionnement in fine de la cellule. Sur la base de cette étude, la fabrication et l'évaluation des propriétés électriques de ces micro-SOFC déposées sur un support poreux de Pt/Al2O3 ont été réalisées
7
Delcuse-Robert, Laura. "Processing effects on the structure and behavior of Nickel based alloys produced by additive manufacturing." Electronic Thesis or Diss., Université de Lorraine, 2021. https://docnum.univ-lorraine.fr/public/DDOC_T_2021_0355_DELCUSE.pdf.
Анотація:
En raison de sa résistance élevée à haute température, l'Inconel 718 est souvent utilisé dans le domaine aérospatial. Grâce à la fabrication additive, de nouvelles structures telles que les structures auxétiques peuvent être produites en Inconel 718 et ainsi offrir de nouvelles opportunités dans de nombreuses applications industrielles. Sous une charge d'impact, la grande capacité d'absorption d'énergie des structures auxétiques offre de nouvelles possibilités, principalement en matière de sécurité dans le domaine routier. Le travail présenté ici est développé autour de cette problématique. Tout d'abord, les paramètres géométriques d'une structure en nid d'abeille inversée ont été optimisés par simulation numérique, en utilisant un plan d’expérience Taguchi et une étude paramétrique. L'influence des paramètres de fusion laser sur lit de poudre - ou Laser Powder Bed Fusion (L-PBF) - a également été abordée sur des structures auxétiques à paroi mince en Inconel 718. La direction d’impression et la densité d'énergie du laser ont été varié afin de déterminer leur effet sur la porosité et la précision d'impression sur des structures minces. Ensuite, le comportement mécanique des structures en nid d’abeille inversée a été étudié en traction et en compression, afin d'identifier la cinétique de déformation de la structure. Pour reproduire ce comportement mécanique, le comportement en compression de l'Inconel 718 imprimé dans les directions d’impressions horizontales (XY) et verticales (ZX) a été étudié en utilisant des conditions quasi-statiques et dynamiques. Les vitesses de déformation appliquées sont comprises entre 10-3 s-1 et 2500 s-1 . Une loi de comportement de Johnson-Cook a été déterminé en tenant compte de l'effet de la direction d’impression sur les propriétés mécaniques. L'anisotropie de l'Inconel 718 imprimé dépend de la direction d’impression, ce qui a été révélée par une étude microstructurale. En utilisant des cartes d'orientat ion EBSD et des micrographies BSE, il a été constaté que la direction de construction horizontale (XY) contient principalement des grains équiaxes par rapport à la présence de grains colonnaires et allongés pour la direction verticale (ZX). De plus, un gradient de microstructure a été observé dans les deux directions d’impression, du bord vers le cœur du matériau, divisé en trois zones : (i) bord, (ii) zone de transition et (iii) zone centrale. Selon l'analyse microstructurale, une nouvelle approche de modélisation de la limite d'élasticité a été développée sur la base de la taille des grains de l'Inconel 718, en fonction de la direction d’impression. Un modèle numérique d’une structure auxétique a été développé sur le logiciel Abaqus, sous un chargement en compression dynamique. La loi de comportement est alors validée par ce modèle , reproduisant le comportement mécanique de la structure auxétique à l’échelle macroscopiqueRegarding its high strength at high temperature, Inconel 718 is widely used in aerospace field. With additive manufacturing, novel structure such as auxetic structure should be produced in Inconel 718 and offered new opportunities in a wide range of industrial application. Under impact loading, the high energy absorption capacity of auxetic material allows new possibilities mainly on safety issues for transport vehicles. The current work is developed through this problematic. First, the geometrical parameters of a re-entrant honeycomb structure were optimised by applying a Taguchi method and a parametrical study on computational modelling. The influence of the laser powder bed fusion parameters (L-PBF) were also tackled on thin-walled cellular structures in Inconel 718. The building direction and the laser energy density were varying to determine their effect on the porosity and print accuracy on thin strut. Then, the mechanical behaviour of the optimised re-entrant honeycomb structures was studied under tension and compression loading to identify the kinetic of deformation of the structure. To reproduce this mechanical behaviour, the compression behaviour of the Inconel 718 printed into horizontal (XY) and vertical (ZX) building direction was investigated using quasi-static and dynamic strain rates, between 10-3 s-1 and 2500 s-1. A Johnson-Cook model was determined considering the effect of the building direction on the mechanical properties. The anisotropy of the printed Inconel 718 depends on the building direction and was revealed by a microstructural study. By using EBSD orientation map and BSE micrographs, it was found that the horizontal building direction (XY) mainly provided equiaxed grain as compared to columnar grain for vertical building direction (ZX). In addition, a microstructure gradient was observed for both building directions from the border to the volume, divided into three zones (i) border, (ii) transition and (iii) centre. According to the microstructural analysis, a novel modelling approach on the yield stress was developed based on the grain size of the Inconel 718. A numerical model of the auxetic structure was developed using Abaqus software, under dynamic compression loading. The behaviour law of the printed Inconel 718 is then validated by this model, reproducing the mechanical behaviour of the auxetic structure at the macroscopic scale
8
D'Agostino, Marco Valerio. "Generalized continua and applications to finite deformations of quasi-inextensible fiber reinforcements." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0061/document.
Анотація:
La microstructure des matériaux constitue un outil essentiel pour optimiser les propriétés mécaniques des structures et ainsi améliorer leurs performances. Les modèles de Cauchy ne sont pas toujours adaptés à la description de la réponse dynamique de certains matériaux microstructurés montrant des comportements mécaniques exotiques. Les théories de milieux continus généralisés peuvent être de bonnes candidates pour modéliser ces matériaux d’une façon plus précise et plus réaliste, aussi bien en statique qu’en dynamique, puisqu’elles peuvent décrire, même d’une façon simplifiée, la manifestation macroscopique de la présence d’une microstructure. Ce manuscrit est organisé comme suit : - Dans le chapitre 1 nous introduisons les aspects généraux de la mécanique des renforts fibreux.- Dans le chapitre 2 nous rappelons certains concepts fondamentaux concernant la mécanique des milieux continus classiques. De plus, nous introduisons les théories de deuxième gradient à l’aide du Principe des Travaux Virtuels.- Dans le chapitre 3 nous nous proposons de présenter une première modélisation des renforts fibreux de composites en mettant en place des modèles numériques discrets. Cette modélisation discrète permet de rendre compte de certains effets de la microstructure des renforts fibreux sur leur comportement macroscopique global. En particulier, il sera montré que la flexion locale des mèches à l’échelle mesoscopique a un effet non-négligeable sur le comportement macroscopique global de ces matériaux. Dans un deuxième moment nous introduisons une modélisation continue de deuxième gradient pour la description des mêmes matériaux et nous montrons que les termes d’ordre supérieur permettent une description satisfaisante des effets de flexion locale sur-cités.- Dans le chapitre 4 on particularise le cadre général de la mécanique des milieux continus introduit dans le chapitre 2 au cas particulier des milieux continus 2D. On mettra un accent fort sur l’interprétation géométrique des mesures de déformation de deuxième gradient qui seront directement reliées aux courbures dans le plan de certaines lignes matérielles. Ces lignes matérielles seront ensuite interprétées dans les chapitres suivantes comme décrivant les mèches des renforts fibreux de composites qu’on se propose d’étudier.- Dans le chapitre 5 nous introduisons une hypothèse cinématique forte sur les déformations admissibles, en supposant que les mèches du renfort considéré sont inextensibles. Cette hypothèse nous permettra de construire un modèle simplifié de premier gradient pour le comportement des renforts de composites 2D qui est encore représentatif de leur comportement mécanique. Une méthode numérique permettant de montrer certaines solutions concernant le cas du bias extension test est codée en Mathematica et les résultats obtenus sont discutésDered materials in the simplest and more effective way. However, there are some cases in which the considered materials are heterogeneous even at relatively large scales and, as a consequence, the effect of microstructure on the overall mechanical behavior of the medium cannot be neglected. In such situations, Cauchy continuum theory may not be useful to fully describe the mechanical behavior of considered materials. It is in fact well known that such continuum theory is not able to catch significant phenomena related to concentrations of stress and strain and to specific deformation patterns in which high gradients of deformation occur and which are, in turn, connected to particular phenomena which take place at lower scales. Generalized continuum theories may be good candidates to model such micro-structured materials in a more appropriate way since they are able to account for the description of the macroscopic manifestation of the presence of microstructure in a rather simplified way. The present manuscript is organized as follows: In ch.1 a general description of fibrous composite reinforcements is given. In ch.2 some fundamental issues concerning classical continuum mechanical models are recalled. In ch.3 we start analyzing some discrete and continuum models for the description of the mechanical behavior of 2D woven composites. At this stage of the manuscript, we want to show how some discrete numerical simulations allowed us to unveil some very special deformation modes related to the effect of the local bending of fibers on the overall macroscopic deformation of fibrous composite reinforcements. Such discrete simulations showed rather clearly that microscopic bending of the fibers cannot be neglected when considering the deformation of fibrous composite reinforcements. For this reason, we subsequently introduced a continuum model which is able to account for such microstructure-related effects by means of second gradient terms appearing in the strain energy density. In ch.4 we reduce the general continuum mechanical framework introduced in ch.2 to the particular case of 2D continua. In ch.5 we introduce a strong kinematical hypothesis on the admissible deformations, assuming that the yarns composing the woven reinforcements are inextensible
9
Benrabah, Imed-Eddine. "Développement d’alliages métalliques à gradient de composition pour l’exploration combinatoire des microstructures." Thesis, Université Grenoble Alpes, 2021. http://www.theses.fr/2021GRALI005.
Анотація:
La transformation de l'austénite en ferrite dans les aciers présente un intérêt considérable pour le contrôle des propriétés finales des aciers, en particulier des aciers à haute résistance (AHSS) tels que l'acier dual phase (DP). Malgré les efforts considérables déployés pour comprendre les mécanismes qui contrôlent la cinétique de formation de la ferrite, le rôle des éléments substitutionnels pendant la croissance de la ferrite et leur interaction avec l'interface de migration α/γ restent peu clair. Plusieurs modèles ont été développés pour décrire la cinétique de croissance de la ferrite dans les systèmes ternaires et les systèmes d’ordre supérieur. Les modèles ‘solute drag’ ont été utilisés avec succès pour prédire la cinétique de transformation pour plusieurs solutés et à de nombreuses compositions et températures dans les systèmes ternaires. Cependant, l'extension de ce modèle aux systèmes d'ordre supérieur a mis en évidence un comportement complexe de l'interaction entre les différents éléments interstitiels et substitutionnels à l'interface. La validation des modèles développés nécessite une étude expérimentale de l'effet de la composition et de la température sur la cinétique de croissance. L'objectif de cette contribution est de présenter une méthodologie combinatoire à haut débit complète pour accélérer l'étude l’effet de la concentration des solutés sur la transformation austénite-ferrite. Il convient toutefois de noter que cette nouvelle méthodologie pourrait être utilisée pour étudier toute autre transformation de phase dans tout autre alliage métallique. L'essence de la méthodologie est de fabriquer des matériaux avec des gradients de composition macroscopiques, et d'effectuer des expériences in situ de diffraction des rayons X à haute énergie, résolues dans le temps et dans l'espace, pour enregistrer la cinétique de transformation de phases austénite-ferrite en de nombreux points de l'espace de composition. Des couples de diffusion contenant des gradients de soluté à l'échelle millimétrique et une teneur en carbone presque constante ont été générés en utilisant la présente méthodologie et utilisés pour étudier la cinétique de croissance de la ferrite à des températures intercritiques en utilisant des expériences in situ de diffraction des rayons X à haute énergie. Pendant 4 jours d'expériences, plus de 1500 cinétiques ont été mesurées pour différentes compositions et à différentes températures. Cet ensemble de données d'une taille sans précédent a été utilisé pour valider une version modifiée du modèle ‘three-jump solute drag’ pour les systèmes ternaires et quaternaires. Les calculs du modèle correspondent parfaitement à la cinétique de transformation expérimentale à toutes les températures étudiées et sur presque toutes les plages de composition étudiées de Si, Cr, Mn, Ni et Mo, contrairement aux résultats des modèles de para-équilibre (PE) et de partitionnement négligeable à l'équilibre local (LENP). En outre, il a été démontré que l'étalonnage des paramètres thermodynamiques dans les systèmes ternaires reste valable dans les systèmes quaternaires, ouvrant la voie à la modélisation de la transformation dans les systèmes d'ordre supérieurThe transformation of austenite into ferrite in steels is of considerable interest in controlling the final properties of steels, in particular Advanced High-Strength Steels (AHSS) such as Dual Phase (DP) steel. Despite tremendous efforts in understanding the mechanisms controlling ferrite formation, the role of substitutional elements during ferrite growth and their interaction with the migrating α/γ interface remain unclear. Several models have been developed to describe ferrite growth kinetics in ternary and higher systems. The solute drag based models have been successfully used to predict kinetics for multiple substitutional solutes, compositions and temperatures in ternary systems. However, the extension of this model to higher order systems highlighted a complex behavior of the interaction between the different interstitial and substitutional elements at the interface. Validation of the developed models requires an experimental study of the effect of both composition and temperature on growth kinetics. The aim of this contribution is to present a complete combinatorial high-throughput methodology to accelerate the investigation of the dependency of ferrite growth kinetics on substitutional composition in alloy steels. It is noteworthy, however, that this new methodology could be used to study any other phase transformation in any other metallic alloy. The essence of the methodology is to fabricate materials with macroscopic composition gradients, and to perform time- and space-resolved in situ high-energy X-ray diffraction experiments to gather the austenite-to-ferrite phase transformation kinetics in many points of the compositional space. Diffusion couples containing millimeter-scale solute gradients and an almost constant carbon content were generated using the present methodology and used to study ferrite growth kinetics at inter-critical temperatures using in-situ high-energy X-ray diffraction experiments. During 4 days of experiments, more than 1500 kinetics were gathered for different compositions and at different temperatures. This dataset of unprecedented size was used validate a modified version of the three-jump solute drag model for both ternary and quaternary systems. The model calculations matched experimental transformation kinetics at all investigated temperatures and over almost all the investigated composition ranges of Si, Cr, Mn, Ni, and Mo, contrary to results from para-equilibrium (PE) and local equilibrium negligible partitioning (LENP) models. Additionally, it was demonstrated that the calibration of thermodynamic parameters in ternary systems held true in quaternary systems, paving the way towards modeling of the transformation in higher-order systems
10
Mohanty, Rashmi. "Phase-Field Simulation of Microstructural Development Induced by Interdiffusion Fluxes Under Multiple Gradients." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4182.
Анотація:
The diffuse-interface phase-field model is a powerful method to simulate and predict mesoscale microstructure evolution in materials using fundamental properties of thermodynamics and kinetics. The objective of this dissertation is to develop phase-field model for simulation and prediction of interdiffusion behavior and evolution of microstructure in multiphase binary and ternary systems under composition and/or temperature gradients. Simulations were carried out with emphasis on multicomponent diffusional interactions in single-phase system, and microstructure evolution in multiphase systems using thermodynamics and kinetics of real systems such as Ni-Al and Ni-Cr-Al. In addition, selected experimental studies were carried out to examine interdiffusion and microstructure evolution in Ni-Cr-Al and Fe-Ni-Al alloys at 1000°C. Based on Onsager’s formalism, a phase-field model was developed for the first time to simulate the diffusion process under an applied temperature gradient (i.e., thermotransport) in single- and two-phase binary alloys.
Development of concentration profiles with uphill diffusion and the occurrence of zeroflux planes were studied in single-phase diffusion couples using a regular solution model for a hypothetical ternary system. Zero-flux plane for a component was observed to develop for diffusion couples at the composition that corresponds to the activity of that component in one of the terminal alloys. Morphological evolution of interphase boundary in solid-to-solid two-phase diffusion couples (fcc-γ vs. B2-β) was examined in Ni-Cr-Al system with actual thermodynamic data and concentration dependent chemical mobility. With the instability introduced as a small initial compositional fluctuation at the interphase boundary, the evolution of the interface morphology was found to vary largely as a function of terminal alloys and related composition dependent chemical mobility. In a binary Ni-Al system, multiphase diffusion couples of fcc-γ vs. L12-γ′, γ vs. γ+γ′ and γ+γ′ vs. γ+γ′ were simulated with alloys of varying compositions and volume fractions of second phase (i.e., γ′). Chemical mobility as a function of composition was employed in the study with constant gradient energy coefficient, and their effects on the final interdiffusion microstructure was examined. Interdiffusion microstructure was characterized by the type of boundaries formed, i.e. Type 0, Type I, and Type II boundaries, following various experimental observations in literature and thermodynamic considerations. Volume fraction profiles of alloy phases present in the diffusion couples were measured to quantitatively analyze the formation or dissolution of phases across the boundaries. Kinetics of dissolution of γ′ phase was found to be a function of interdiffusion coefficients that can vary with composition and temperature.
The evolution of interdiffusion microstructures in ternary Ni-Cr-Al solid-to-solid diffusion couples containing fcc-γ and γ+β (fcc+B2) alloys was studied using a 2D phase-field model. Alloys of varying compositions and volume fractions of the second phase (β) were used to simulate the dissolution kinetics of the β phase. Semi-implicit Fourier-spectral method was used to solve the governing equations with chemical mobility as a function of compositions. The simulation results showed that the rate of dissolution of the β phase (i.e., recession of β+γ twophase region) was dependent on the composition of the single-phase γ alloy and the volume fraction of the β phase in the two-phase alloy of the couple. Higher Cr and Al content in the γ alloy and higher volume fraction of β in the γ+β alloy lower the rate of dissolution. Simulated results were found to be in good agreement with the experimental observations in ternary Ni-Cr- Al solid-to-solid diffusion couples containing γ and γ+β alloys.
For the first time, a phase-field model was developed to simulate the diffusion process under an applied temperature gradient (i.e., thermotransport) in multiphase binary alloys. Starting from the phenomenological description of Onsager’s formalism, the field kinetic equations are derived and applied to single-phase and two-phase binary system. Simulation results show that a concentration gradient develops due to preferential movement of atoms towards the cold and hot end of an initially homogeneous single-phase binary alloy subjected to a temperature gradient. The temperature gradient causes the redistribution of both constituents and phases in the two-phase binary alloy. The direction of movement of elements depends on their atomic mobility and heat of transport values.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science & Engr PhD
Книги з теми "Microstructural gradient":
1
Patrick, Dunn, and United States. National Aeronautics and Space Administration., eds. An evaluation of a coupled microstructural approach for the analysis of functionally graded composites via the finite-element method. [Washington, DC: National Aeronautics and Space Administration, 1995.
2
Zhou, Liucheng, and Weifeng He. Gradient Microstructure in Laser Shock Peened Materials. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1747-8.
3
Rhaipu, Soranat. The effect of microstructural gradients on the superplastic forming of TI-6AL-4V. Birmingham: University of Birmingham, 2000.
4
J, Roth Don, and Lewis Research Center, eds. Scaling up the single transducer thickness-independent ultrasonic imaging method for accurate characterization of microstructural gradients in monolithic and composite tubular structures. [Cleveland, Ohio]: National Aeronautics and Space Administration, Lewis Research Center, 1998.
5
P, Gangloff R., Kelly R. G, and United States. National Aeronautics and Space Administration., eds. NASA-UVa light aerospace alloy and structures technology program, LA²ST.: Research on materials for the high speed civil transport. [Washington, DC: National Aeronautics and Space Administration, 1997.
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P, Gangloff R., Kelly Robert G, and United States. National Aeronautics and Space Administration., eds. NASA-UVa light aerospace alloy and structures technology program, LA²ST.: Research on materials for the high speed civil transport. [Washington, DC: National Aeronautics and Space Administration, 1997.
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P, Gangloff R., Kelly Robert G, and United States. National Aeronautics and Space Administration., eds. NASA-UVa light aerospace alloy and structures technology program, LA²ST.: Research on materials for the high speed civil transport. [Washington, DC: National Aeronautics and Space Administration, 1997.
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P, Gangloff R., and United States. National Aeronautics and Space Administration., eds. NASA-UVa light aerospace alloy and structures technology program (LA²ST): A progress report July 1, 1994 to December 31, 1994. Charlottesville, VA: School of Engineering & Applied Center, 1995.
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P, Gangloff R., and United States. National Aeronautics and Space Administration., eds. NASA-UVa light aerospace alloy and structures technology program (LA²ST): A progress report July 1, 1994 to December 31, 1994. Charlottesville, VA: School of Engineering & Applied Center, 1995.
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P, Gangloff R., and United States. National Aeronautics and Space Administration., eds. NASA-UVa light aerospace alloy and structures technology program (LA²ST): A progress report July 1, 1994 to December 31, 1994. Charlottesville, VA: School of Engineering & Applied Center, 1995.
Частини книг з теми "Microstructural gradient":
1
Eastman, J. A., G. Soyez, G. R. Bai, and L. J. Thompson. "Nanostructured Materials for Microstructural Control of Thermal Properties." In Functional Gradient Materials and Surface Layers Prepared by Fine Particles Technology, 183–97. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-010-0702-3_20.
2
Zhou, Liucheng, and Weifeng He. "Gradient Microstructure Characteristics and the Formation Mechanism in Titanium Alloy Subjected to LSP." In Gradient Microstructure in Laser Shock Peened Materials, 41–76. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1747-8_3.
3
Zhou, Liucheng, and Weifeng He. "Improvement of High Temperature Fatigue Performance in Ni-Based Alloys by LSP-Induced Gradient Microstructures." In Gradient Microstructure in Laser Shock Peened Materials, 103–38. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1747-8_5.
4
Zhou, Liucheng, and Weifeng He. "Study on the Compound Process of LSP and the Strengthening Mechanism on Aero-Engine Blades." In Gradient Microstructure in Laser Shock Peened Materials, 179–227. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1747-8_7.
5
Zhou, Liucheng, and Weifeng He. "Characteristics of Laser-Induced Plasma Shock Wave in Metal Materials." In Gradient Microstructure in Laser Shock Peened Materials, 15–40. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1747-8_2.
6
Zhou, Liucheng, and Weifeng He. "Mechanical Behavior and the Strengthening Mechanism of LSP-Induced Gradient Microstructure in Metal Materials." In Gradient Microstructure in Laser Shock Peened Materials, 139–77. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1747-8_6.
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Zhou, Liucheng, and Weifeng He. "General Introduction." In Gradient Microstructure in Laser Shock Peened Materials, 1–14. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1747-8_1.
8
Zhou, Liucheng, and Weifeng He. "Improvement of High Cycle Fatigue Performance in the Titanium Alloy by LSP-Induced Gradient Microstructure." In Gradient Microstructure in Laser Shock Peened Materials, 77–101. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1747-8_4.
9
Sorrell, Charles C., Naser Ehsani, Andrew J. Ruys, and Owen C. Standard. "Absence of Microwave Effect in Ceramics: Precise Temperature, Thermal Gradient, and Densification Determination in A Proportional-Power Microwave Furnace." In Ceramic Microstructures, 471–86. Boston, MA: Springer US, 1998. http://dx.doi.org/10.1007/978-1-4615-5393-9_46.
10
Tax, Chantal M. W., Elena Kleban, Muhamed Baraković, Maxime Chamberland, and Derek K. Jones. "Magnetic Resonance Imaging of $$T_2$$- and Diffusion Anisotropy Using a Tiltable Receive Coil." In Mathematics and Visualization, 247–62. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-56215-1_12.
Анотація:
AbstractThe anisotropic microstructure of white matter is reflected in various MRI contrasts. Transverse relaxation rates can be probed as a function of fibre-orientation with respect to the main magnetic field, while diffusion properties are probed as a function of fibre-orientation with respect to an encoding gradient. While the latter is easy to obtain by varying the orientation of the gradient, as the magnetic field is fixed, obtaining the former requires re-orienting the head. In this work we deployed a tiltable RF-coil to study $$T_2$$ T 2 - and diffusional anisotropy of the brain white matter simultaneously in diffusion-$$T_2$$ T 2 correlation experiments.
Тези доповідей конференцій з теми "Microstructural gradient":
1
Nadeau, Joseph C., and Mauro Ferrari. "Microstructural Optimization of a Functionally Gradient Layer." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0645.
Анотація:
Abstract This paper addresses the microstructural optimization of an infinite, transversely isotropic layer which is free of tractions and subjected to a prescribed thermal gradient. The layer’s microstructure is characterized as a bi-phase composite in the form of a continuous matrix perfectly bonded to embedded spheroidal reinforcements. The microstructural characterization of the FGM is taken to be the volume fraction, aspect ratio and orientation distribution function of the second phase. The composite layer is made functionally gradient by taking the aforementioned parameters to vary through the thickness of the layer. The effective properties of the bi-phase composite are obtained by appropriate homogenization theories. The microstructural parameters are determined such that an objective function, defined in terms of strain energy and curvature, is minimized. Specific results are presented for an aluminum (Al) layer reinforced with silicon carbide (SiC). Comparisons are made to conventional coating technology.
2
Rangarajan, Aswath, and Veera Sundararaghavan. "Design of Microstructure Response Using a Complex Step Plasticity Approach." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-39011.
Анотація:
Microstructure-sensitive design is performed using a newly developed Multiscale Complex Step Method. Algorithmic implementation of the complex-step method is based on conventional multiscale Taylor or FE2 direct model, with the difference being that the microstructural deformation gradient is modeled as a complex number with a small imaginary component. We introduce methods to calculate derivatives of microstructural fields with respect to loading parameters. The sensitivities are used to identify optimal microstructures with desired elastic and plastic properties.
3
Samanta, Avik, Ninggang Shen, Haipeng Ji, Weiming Wang, Hongtao Ding, and Jingjing Li. "Simulations of Microstructure Evolution During Friction Stir Blind Riveting Using a Cellular Automaton Method." In ASME 2017 12th International Manufacturing Science and Engineering Conference collocated with the JSME/ASME 2017 6th International Conference on Materials and Processing. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/msec2017-3034.
Анотація:
Friction stir blind riveting (FSBR) is a novel and highly efficient joining technique for lightweight metal materials, such as aluminum alloys. The FSBR process induced large gradients of plastic deformation near the rivet hole surface and resulted in a distinctive gradient microstructure in this domain. In this study, microstructural analysis is conducted to analyze the final microstructure after the FSBR process. Dynamic recrystallization (DRX) is determined as the dominant microstructure evolution mechanism due to the significant heat generation during the process. To better understand the FSBR process, a two-dimensional Cellular Automaton (CA) model is developed to simulate the microstructure evolution near the rivet hole surface by considering the FSBR process loading condition. To model the significant microstructure change near the rivet hole surface, spatial distributed temporal thermal and mechanical loading conditions are applied to simulate the effect of the large gradient plastic deformation near the hole surface. The distribution grain topography and recrystallization fraction are obtained through the simulations, which agree well with the experimental data. This study presents a reliable numerical approach to model and simulate microstructure evolution governed by DRX under the large plastic deformation gradient in FSBR.
4
Sanchez, Nuria, Nenad Ilić, and Martin Liebeherr. "Characterization of X80 Grade Linepipe Steel Coil With 24 mm Thickness." In 2012 9th International Pipeline Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ipc2012-90412.
Анотація:
High strength and high toughness at low temperatures on heavy wall thickness skelp is required to build high pressure gas transportation pipelines. Detailed mechanical and microstructural characterization was carried on 24mm thick ArcelorMittal X80 coils in order to identify the microstructure control required to reach high toughness as determined by the shear fracture appearance after DWTT testing. Detailed microstructural characterization through thickness reveals that the microstructure gradient described by a systematic increase of the average grain size between surface and middle thickness of the strip and the increment of the volume fraction of M/A (martensite/ retained austenite) are the key microstructural parameters to control in order to ensure the adequate toughness of the material. The obtained high toughness of the coils indicates that the microstructure, controlled by an optimized rolling and cooling practice, is homogeneous through thickness of heavy wall linepipe grades.
5
Wang, Zhiyu, Christopher Saldana, and Saurabh Basu. "Subsurface Microstructure and Crystallographic Texture in Surface Severe Plastic Deformation Processes." In ASME 2017 12th International Manufacturing Science and Engineering Conference collocated with the JSME/ASME 2017 6th International Conference on Materials and Processing. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/msec2017-2915.
Анотація:
Severe plastic burnishing was investigated as a promising surface severe plastic deformation technique for generating gradient microstructure surfaces. The deformed state of oxygen free high conductivity copper workpieces during the surface deformation process was determined with high-speed imaging, this complemented by microstructure characterization using orientation image microscopy based on electron backscatter diffraction. Varying deformation levels in terms of both magnitude and gradient on the processed surface were achieved through control of the incident tool angle. Refined microstructures, including laminate grains elongated in the velocity direction and equiaxed sub-micron grains were observed in the subsurface and were found to be controlled by the combined effects of strain and strain rate in the surface deformation process. Additionally, crystallographic texture evolutions were characterized, showing typical shear textures predominately along the <110> partial fiber. The rotation of texture from original ideal orientation positions was related directly to the deformation history produced by sliding process. Based on these observations, a controllable framework for producing the processed surface with expected mechanical and microstructural responses is suggested.
6
Cuilik, Michael, and Jeffrey M. Rahl. "CRYSTALLOGRAPHIC PREFERRED ORIENTATION AND MICROSTRUCTURAL ANALYSES ACROSS A STRAIN GRADIENT, MAGGIA NAPPE, SWITZERLAND." In GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-308188.
7
Che, Chang, Gong Qian, Xishen Yang, and Xiang Liu. "Microstructural Evolution and High Temperature Failure of T91/TP347H Dissimilar Welds Used in China Plants." In AM-EPRI 2019, edited by J. Shingledecker and M. Takeyama. ASM International, 2019. http://dx.doi.org/10.31399/asm.cp.am-epri-2019p1159.
Анотація:
Abstract Dissimilar metal welds between T91 ferritic steels and TP347H austenitic alloys are commonly used in fossil power plants in China. Premature failure of such dissimilar welds can occur, resulting in unplanned plant outages that can cause huge economic losses. In this article, microstructural evolution of T91/TP347H dissimilar welds after different service conditions were studied, mechanical properties before and after service were also analyzed, a full investigation into the failure cause was carried out. The results show, the dissimilar metal welds in the as-welded condition consists of a sharp chemical concentration gradient across the fusion line, failure is attributed to the steep microstructural and mechanical properties gradients, formation of interfacial carbides that promote creep cavity formation.
8
Li, Dong-Feng, Brian Golden, and Noel P. O’Dowd. "Modelling of Micro-Plasticity Evolution in Crystalline Materials." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97233.
Анотація:
In this work, a micromechanical finite element model is presented to investigate micro-plasticity evolution in crystalline materials, with a comprehensive consideration of microstructural interactions, including morphology-based intragranular stress-strain response and the strain gradient induced scale effect. A dislocation-mechanics based crystal plasticity formulation has been employed to account for slip based inelastic deformation. A polycrystalline model has been constructed using the Voronoi tessellation technique to represent the microstructure of a martensitic power plant steel, P91. The model has been validated through a uniaxial tensile test. The effects of strain gradient have been examined at both macroscopic and microscopic levels and the importance of accounting for strain gradient effects in the prediction of local deformation states is discussed for P91.
9
Bertelsen, Jacob M., and Andrew D. Sommers. "Facilitating Water Droplet Removal From Wind Turbine Blades Using Surface Wettability Gradients." In ASME 2023 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/imece2023-112445.
Анотація:
Abstract A new method is proposed to mitigate ice accretions on wind turbine blades via the creation of a microstructural gradient surface geometry that facilitates spontaneous water droplet motion along the surface. The wettability gradients are formed by laser etching 35μm wide by 35μm deep channels into aluminum to form a surface with a gradually increasing solid area fraction which results in one end of the gradient surface being superhydrophobic and the other end being hydrophilic. Different design permutations are proposed and systematically assessed on the merits of their performance with respect to a baseline flat homogeneous surface and with respect to each other. An analytical model is also derived based on a balance of hysteresis and drag forces to predict the critical airspeed necessary for droplet movement as a function of the droplet size and the intrinsic contact angle of the surface. To date, experimentation has validated the model for the baseline surface and has also demonstrated that, in certain cases, up to 70% lower critical airspeeds are required to initiate droplet motion on these microstructured surfaces as opposed to the homogeneous baseline samples.
10
Abu Al-Rub, Rashid K., and George Z. Voyiadjis. "Modeling the Size and Interface Effects in Thin Metal Film-Substrate Systems Using the Strain Gradient Plasticity." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42020.
Анотація:
It is well-known by now through intensive experimental studies that have been performed at the micron and nano length scales that the material mechanical properties strongly depend on the size of specimen and the microstructural features. The classical continuum mechanics fails to address this problem since no material length scale exists in its constitutive description. On the other hand, nonlocal continuum theories of integral-type or gradient-type have been to a good extent successful in predicting this type of size effect. However, they fail to predict size effects when strain gradients are minimal such as the Hall-Petch effect. This problem is the main focus of this work. The effect of the material microstructural interfaces increase as the surface-to-volume ratio increases. It is shown in this work that interfacial effects have a profound impact on the scale-dependent plasticity encountered in micro/nano-systems. This is achieved by developing a higher-order gradient-dependent plasticity theory that enforces microscopic boundary conditions at interfaces and free surfaces. These nonstandard boundary conditions relate the microtraction stress at the interface to the interfacial energy. Application of the proposed framework to size effects in shear loading of a thin-film on an elastic substrate is presented. Three film-interface conditions are modeled: soft, intermediate, and hard interfaces.
Звіти організацій з теми "Microstructural gradient":
1
Castelluccio, Gustavo, Hojun Lim, John Emery, and Corbett Battaile. Fracture Toughness of Microstructural Gradients. Office of Scientific and Technical Information (OSTI), October 2016. http://dx.doi.org/10.2172/1761823.
2
McNeil, Anne J. New Microstructures for Old Monomers: Syntheses of Gradient pi-Conjugated Copolymers. Fort Belvoir, VA: Defense Technical Information Center, June 2010. http://dx.doi.org/10.21236/ada534918.
3
Burton R. Patterson. Effect of Casting Conditions and Composition on Microstructural Gradients in Roll Cast Aluminum Alloys. Office of Scientific and Technical Information (OSTI), May 2008. http://dx.doi.org/10.2172/927781.
4
Wootton, K. P., Z. Wu, B. M. Cowan, A. Hanuka, I. V. Makasyuk, E. A. Peralta, K. Soong, R. L. Byer, and R. J. England. Observation of 690 MV m-1 Electron Accelerating Gradient with a Laser-Driven Dielectric Microstructure. Office of Scientific and Technical Information (OSTI), January 2016. http://dx.doi.org/10.2172/1234198.
5
Oliynyk, Kateryna, and Matteo Ciantia. Application of a finite deformation multiplicative plasticity model with non-local hardening to the simulation of CPTu tests in a structured soil. University of Dundee, December 2021. http://dx.doi.org/10.20933/100001230.
Анотація:
In this paper an isotropic hardening elastoplastic constitutive model for structured soils is applied to the simulation of a standard CPTu test in a saturated soft structured clay. To allow for the extreme deformations experienced by the soil during the penetration process, the model is formulated in a fully geometric non-linear setting, based on: i) the multiplicative decomposition of the deformation gradient into an elastic and a plastic part; and, ii) on the existence of a free energy function to define the elastic behaviour of the soil. The model is equipped with two bonding-related internal variables which provide a macroscopic description of the effects of clay structure. Suitable hardening laws are employed to describe the structure degradation associated to plastic deformations. The strain-softening associated to bond degradation usually leads to strain localization and consequent formation of shear bands, whose thickness is dependent on the characteristics of the microstructure (e.g, the average grain size). Standard local constitutive models are incapable of correctly capturing this phenomenon due to the lack of an internal length scale. To overcome this limitation, the model is framed using a non-local approach by adopting volume averaged values for the internal state variables. The size of the neighbourhood over which the averaging is performed (characteristic length) is a material constant related to the microstructure which controls the shear band thickness. This extension of the model has proven effective in regularizing the pathological mesh dependence of classical finite element solutions in the post-localization regime. The results of numerical simulations, conducted for different soil permeabilities and bond strengths, show that the model captures the development of plastic deformations induced by the advancement of the cone tip; the destructuration of the clay associated with such plastic deformations; the space and time evolution of pore water pressure as the cone tip advances. The possibility of modelling the CPTu tests in a rational and computationally efficient way opens a promising new perspective for their interpretation in geotechnical site investigations.