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1
Subramaniyan, Jaya. "Extrusion of 2024 aluminium alloy sections." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47677.
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2
Bendo, Demetrio Ketner. "Cryomilling and Spark Plasma Sintering of 2024 Aluminium Alloy." Doctoral thesis, Università degli studi di Trento, 2011. https://hdl.handle.net/11572/369246.
Full textAbstract:
Aluminium alloys are characterized by a low specific weight, which make them highly interesting for structural applications. Mechanical properties are lower than those of steels, so the possibility to obtain an increase by means of the structural refining (either nano- or ultra-fine grained structure) would extend their applications in several fields.
Bulk nanocrystalline metals and alloys can be produced by high energy milling of powders and their consolidation by sintering techniques characterized by a low thermal load in order to minimize grain growth. This is an alternative approach to other methods based on severe plastic deformation, with the advantage of obtaining near-net shape parts, within the limits of the Powder Metallurgy (PM) route. Even in the case of the part cannot be obtained directly a preform can be produced by Powder Metallurgy and finished by hot working. In this case, Powder Metallurgy is used to produce preforms with geometry closer to the final one than that attainable by other technologies, reducing production costs and raw material consumption.
It is well known that nanostructure (D < 100 nm) of Al alloys can be obtained by high energy milling technique. During milling, the grain size is determined by equilibrium between recovery and formation of defects due to heavy plastic deformation. Face centered cubic (FCC) materials, as Al and alloys, are difficult to reduce by mechanical milling. The opposite occurs with body centred cubic (BCC) and hexagonal close packet (HCP) metals due to relatively defects accumulation and difficult of fast recovery kinetics.
A valid alternative is the cryogenic milling, where the powders are milled in slurry formed with liquid nitrogen. Cryomilling takes advantage due to low temperature of the liquid nitrogen that either suppresses or limits recovery and recrystallization and leads to finer grain structure faster. In addition cryogenic milling does not require use of process control agent (PCA) that can contaminate the powder with carbon and oxygen.
A very important factor to preserve the nanostructure of a material is its thermal stability that depends on the balance between driving and resisting forces. It is well known that the smaller the grain size, the bigger the tendency to grain growth. In most cases, the thermal stability of a nanostructure depends on the lattice defects stored between and within grains, and on the particles such as nitrides and oxides precipitated at the grain boundaries. It is really important achieve an equilibrium between grain size and thermal stability of the material to avoid grain growth on sintering. Moreover, if the powder particles are very fine, sintering becomes hard because of the oxide layer that surrounds the particles.
Bulk nanomaterials can be produced through several PM techniques. Hot isostatic press (HIP), dynamic consolidation, hot extrusion and spark plasma sintering (SPS) are effective to achieve a full dense material. In the frame of the near-net shape technologies, SPS is a novel technology that has large potentiality, because of the lower temperature and shorter time required. In this process a pulse electric current flows directly on the powders and a high heating efficiency is offered.
It is known that Al powders are hardly sinterable due to oxide layer on their surface. This layer has to be broken in order to form a solid neck between the particles. SPS has been used to produce nanostructured Al and iron alloys starting from nanostructured powders.
A bimodal microstructure can be formed during SPS sintering due to the localized overheating generated by the sparks and low thermal stability of the material. It is well known that a bimodal microstructure reveals an improvement of ductility which is the most critical characteristics of nanostructured metals. In a simplistic view, ultra-fine/nano crystallites are responsible for high strength and micrometric grains provide increased ductility. Additional strategies of ductility improvement provides deformation at low temperatures/high strain rates, which furnishes accumulation of dislocations within nanocrystalline/UFG, resulting in increased strain hardening and enhancement of strain rate sensitivity of the flow stress.
Hot workability of metals depends on several parameters. Temperature and strain rate affect the flow stress and the strain rate sensitivity. The former increases on decreasing grain size, until the deformation process is determined by dislocation motion. In FCC materials, particularly in Al and its alloys, refining grains to UFG level promotes an increase in strain rate sensitivity. The hot workability is usually defined as the quantity of deformation that a material can undergo without cracking and reaching desirable deformed microstructures at a given temperature and strain rate. Improving workability means increasing the processing ability and the properties of the materials. Hot workability can be studied by the approach of the power dissipation maps.
In this PhD work, the production of nanometric Al 2024 alloy powder by cryomilling, ultra-fine grained/micrometric material consolidated by SPS, and its further deformability at high temperature was studied. The results are presented in three chapters.
Chapter 1 reports the methodology to obtain the nanostructured 2024 alloy powder. Many aspects such as the evolution of the microstructure, the role of liquid nitrogen during milling and the thermal stability are studied in order to have an insight on the kinetics (1). The study of the thermal stability of the nanostructured powder is presented, as well.
Chapter 2 describes the SPS experiments of the as-atomized and as-milled powders and the characterization of the consolidated material.
Chapter 3 reports the hot compression experiments on the atomized and milled samples, and discusses the differences in the deformation behaviour on the basis of the starting microstructure and of its evolution during deformation.
3
Bendo, Demetrio Ketner. "Cryomilling and Spark Plasma Sintering of 2024 Aluminium Alloy." Doctoral thesis, University of Trento, 2011. http://eprints-phd.biblio.unitn.it/532/1/PhD_Thesis_Ketner_B_Demetrio.pdf.
Full textAbstract:
Aluminium alloys are characterized by a low specific weight, which make them highly interesting for structural applications. Mechanical properties are lower than those of steels, so the possibility to obtain an increase by means of the structural refining (either nano- or ultra-fine grained structure) would extend their applications in several fields.
Bulk nanocrystalline metals and alloys can be produced by high energy milling of powders and their consolidation by sintering techniques characterized by a low thermal load in order to minimize grain growth. This is an alternative approach to other methods based on severe plastic deformation, with the advantage of obtaining near-net shape parts, within the limits of the Powder Metallurgy (PM) route. Even in the case of the part cannot be obtained directly a preform can be produced by Powder Metallurgy and finished by hot working. In this case, Powder Metallurgy is used to produce preforms with geometry closer to the final one than that attainable by other technologies, reducing production costs and raw material consumption.
It is well known that nanostructure (D < 100 nm) of Al alloys can be obtained by high energy milling technique. During milling, the grain size is determined by equilibrium between recovery and formation of defects due to heavy plastic deformation. Face centered cubic (FCC) materials, as Al and alloys, are difficult to reduce by mechanical milling. The opposite occurs with body centred cubic (BCC) and hexagonal close packet (HCP) metals due to relatively defects accumulation and difficult of fast recovery kinetics.
A valid alternative is the cryogenic milling, where the powders are milled in slurry formed with liquid nitrogen. Cryomilling takes advantage due to low temperature of the liquid nitrogen that either suppresses or limits recovery and recrystallization and leads to finer grain structure faster. In addition cryogenic milling does not require use of process control agent (PCA) that can contaminate the powder with carbon and oxygen.
A very important factor to preserve the nanostructure of a material is its thermal stability that depends on the balance between driving and resisting forces. It is well known that the smaller the grain size, the bigger the tendency to grain growth. In most cases, the thermal stability of a nanostructure depends on the lattice defects stored between and within grains, and on the particles such as nitrides and oxides precipitated at the grain boundaries. It is really important achieve an equilibrium between grain size and thermal stability of the material to avoid grain growth on sintering. Moreover, if the powder particles are very fine, sintering becomes hard because of the oxide layer that surrounds the particles.
Bulk nanomaterials can be produced through several PM techniques. Hot isostatic press (HIP), dynamic consolidation, hot extrusion and spark plasma sintering (SPS) are effective to achieve a full dense material. In the frame of the near-net shape technologies, SPS is a novel technology that has large potentiality, because of the lower temperature and shorter time required. In this process a pulse electric current flows directly on the powders and a high heating efficiency is offered.
It is known that Al powders are hardly sinterable due to oxide layer on their surface. This layer has to be broken in order to form a solid neck between the particles. SPS has been used to produce nanostructured Al and iron alloys starting from nanostructured powders.
A bimodal microstructure can be formed during SPS sintering due to the localized overheating generated by the sparks and low thermal stability of the material. It is well known that a bimodal microstructure reveals an improvement of ductility which is the most critical characteristics of nanostructured metals. In a simplistic view, ultra-fine/nano crystallites are responsible for high strength and micrometric grains provide increased ductility. Additional strategies of ductility improvement provides deformation at low temperatures/high strain rates, which furnishes accumulation of dislocations within nanocrystalline/UFG, resulting in increased strain hardening and enhancement of strain rate sensitivity of the flow stress.
Hot workability of metals depends on several parameters. Temperature and strain rate affect the flow stress and the strain rate sensitivity. The former increases on decreasing grain size, until the deformation process is determined by dislocation motion. In FCC materials, particularly in Al and its alloys, refining grains to UFG level promotes an increase in strain rate sensitivity. The hot workability is usually defined as the quantity of deformation that a material can undergo without cracking and reaching desirable deformed microstructures at a given temperature and strain rate. Improving workability means increasing the processing ability and the properties of the materials. Hot workability can be studied by the approach of the power dissipation maps.
In this PhD work, the production of nanometric Al 2024 alloy powder by cryomilling, ultra-fine grained/micrometric material consolidated by SPS, and its further deformability at high temperature was studied. The results are presented in three chapters.
Chapter 1 reports the methodology to obtain the nanostructured 2024 alloy powder. Many aspects such as the evolution of the microstructure, the role of liquid nitrogen during milling and the thermal stability are studied in order to have an insight on the kinetics (1). The study of the thermal stability of the nanostructured powder is presented, as well.
Chapter 2 describes the SPS experiments of the as-atomized and as-milled powders and the characterization of the consolidated material.
Chapter 3 reports the hot compression experiments on the atomized and milled samples, and discusses the differences in the deformation behaviour on the basis of the starting microstructure and of its evolution during deformation.
4
Ganguly, Supriyo. "Non-destructive measurement of residual stresses in welded aluminium 2024 airframe alloy." Thesis, n.p, 2004. http://ethos.bl.uk/.
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5
Elabar, Dawod. "Effect of sulphate impurity in chromic acid anodizing of aluminium and aluminium alloy." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/effect-of-sulphate-impurity-in-chromic-acid-anodizing-of-aluminium-and-aluminium-alloy(ec562f6a-6bc9-4bb4-9eee-468d539f90a2).html.
Full textAbstract:
In this work, the nucleation and growth of pores in anodic films formed on aluminium in chromic acid and the effect of low levels of sulphate impurity in the anodizing bath on the formation of the films on aluminium and AA 2024 alloy are investigated. The sulphate concentrations considered include levels within specified limits for industrial processing. The anodizing is carried out either potentiostatically or by stepping the voltage. The films are examined by scanning electron microscopy, transmission electron microscopy and atomic force microscopy to determine the pore spacing, pore population densities, pore diameters and film thicknesses. Film compositions were determined using energy-dispersive X-ray spectroscopy, Rutherford backscattered microscopy and nuclear reaction analysis. In order to investigate the mechanism of pore formation, two tracer methods are employed. In one method, anodic films are formed first in an arsenate electrolyte in the second method, a tungsten tracer band deposited by magnetron sputtering. The behaviours of arsenic and the tungsten are investigated during the subsequent anodizing in chromic acid. The results suggest that the initiation and growth of pores in occurred as a result of electric field assisted chemical dissolution. The effect of sulphate impurity in the chromic acid is investigated using electrolytes with different sulphate content. In the initial stages of anodizing aluminium at 100 V, sulphate impurity at a level of 38 ppm in the chromic acid is shown to lead to significant incorporation of sulphate ions into the anodic film, a lower current density, a smaller cell size and less feathering of the pore walls. In addition, the efficiency of film formation is increased. In later stages of anodizing, the growth of larger pores and cells, leads to a duplex film morphology, with finer pores in the outer region. The change in pore size correlates with a reduction in the incorporation of sulphate into the film. From the results of sequential anodizing experiments, it is suggested that incorporated sulphate ions generate a space charge layer, which has an important role in determining the current density. The effects of higher sulphate concentrations up to 3000 ppm are investigated, which are shown to significantly affect the current density and the pore diameter. Anodizing of aluminium and AA 2024 alloy was also carried out according to industrial practice. The results show that there is significant effect of sulphur impurity on the film thickness. Corrosion tests in 3.5 % NaCl solution for the alloy after anodizing in low (smaller or equal to 1.5 ppm) and high (~38 ppm) sulphate-containing chromic acid electrolytes demonstrate a better corrosion resistance with films formed in the latter electrolyte.
6
Efthymiadis, Panos. "Multiscale experimentation & modeling of fatigue crack development in aluminium alloy 2024." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/7735/.
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The objective of this research project is to be able to understand the role of various microstructural features on Fatigue Crack Initiation (FCI) of metallic alloys. By employing a novel experimental set-up, mechanical testing was performed in situ within an SEM chamber, and the deformation of the individual grains was observed real time. A physically-based Crystal Plasticity (CP) model was then developed that accurately predicts the macro and micro mechanical behaviour for Al2024 T3. An experimentally informed FCI criterion was developed that accounts for the effect of local slip bands and the applied local strains. While ‘precious’ insights were given on the small crack growth regime observing the occurring microscale phenomena. FCI is a multiscale process and thus evaluating the microscale does not cover fully the understanding of local deformation and damage. Thus a multiscale DIC process was employed to better understand the macro and mesoscale as well. 3D Digital Image Correlation (DIC) was employed and the strain distributions (at the sample scale) were obtained for various loading conditions. High magnification camera based 2D DIC was then used and the strain measurements were also extracted at clusters of grains. Useful observations were given for the different strain components (εxx, εyy, εxy). Finally the total fatigue lifetime of the component was compared to the modeled FCI for various loading conditions.
7
Boag, Adam Paull, and adam boag@gmail com. "The Relationship Between Microstructure and Stable Pitting Initiation in Aerospace Aluminium Alloy 2024-T3." RMIT University. Applied Science, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20091028.114831.
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Aluminium alloys are essential to a variety of industry sectors, particularly transport, where they are used in the production of cars and aeroplanes. However, aluminium alloys are susceptible to degradation through corrosion which can compromise the integrity of components manufactured from this material. Therefore research into the means by which these alloys degrade is important. This thesis aims to understand how one of the more potentially damaging types of corrosion, known as pitting corrosion, occurs in the important aluminium alloy 2024-T3 (AA2024-T3). In order to study this phenomenon, this thesis first characterises the alloy microstructure in detail, particularly the type and distribution of intermetallic particles since these play an important role in corrosion processes. The microstructure was studied using an electron microprobe analysis of a 5 mm x 5 mm area of AA2024-T3 and some 80,000 particles were characterised. This investigation was one of the most comprehensive studies to date of any aluminium alloy. Of the particles studied, it was found that the major types included the S and θ phases and a number of compositions based around AlCuFeMn and AlCuFeMnSi. Depletion zones were an integral feature of the alloy microstructure. Pair correlation functions were used to determine the degree of clustering and it was found that there was both inter particle as well as intra particle clustering. Inter particle clustering was observed at length scales well beyond 50 µm. A detailed study of corrosion on AA2024-T3 was undertaken by examining the surface after corrosion over a time period spanning 2.5 minutes to 120 minutes. From this investigation, a hierarchy of the localised corrosion was observed as it was very apparent that particles of particular elemental compositions were more susceptible to attack much sooner than other compositions. Larger corrosion attack sites on the surface, which were called co-operative corrosion, were attributed to intermetallic clustering affects and changes in chemical composition such as Cu-enrichment. These results were used to develop a detailed model of the initiation of stable pitting corrosion in AA2024-T3, which will lead to a better understanding on how to prevent pitting attack on commercially important aluminium alloys. AA2024-T3 is rarely used in the polished state, for real world applications is it generally finished by mechanical or chemical processing. In the final part of this thesis, the influence of clusters on metal finishing was examined using a standard aluminium chemical deoxidiser. It was found that the etch rate of this deoxidiser increased dramatically with the increase in temperature. Under certain processing conditions only the intermetallic particles are etched out and these retain the history of the spatial distribution of the clustering of the intermetallic particles. This leaves a cluster of 'holes' which could trap metal finishing solution and lead to severe subsurface attack
8
Asquith, David Thomas. "Residual stress and fatigue in cold-worked, hard-coated 2024-T351 aluminium alloy." Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486777.
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Due to the continued demand for high performance, light-weight components in many areas of engineering, researchers strive to enhance characteristics to satisfy these needs. A synergistic approach to performance enhancement. of aluminium alloys has been investigated through combined cold-work and hard coating thereby affording increased performance in teIflls of both fatigue and surface hardness. With an' emphasis on coldwork processing, two different methods of introducing surface compressive residual stresses in this manner have been used. This leads to an interest in the influence of residual stress in the hard coated aluminium on its behaviour. In particular, the characterisation of residual stress states in the modified materials with specific-interest in the evolution of triaxial stresses with the treatment process steps has been studied. This is combined with materials characterisation in form of microstructure, micro-hardness, phase composition and corrosion behaviour to complete the evaluation of duplex treatments.
9
Elaish, Reafat. "Influences of fluorine species on the anodizing behaviour of aluminium and AA 2024-T3 alloy." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/influences-of-fluorine-species-on-the-anodizing-behaviour-of-aluminium-and-aa-2024t3-alloy(7849513e-31b6-4f71-a6ee-126ee5221321).html.
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The present study investigates the effect of fluorine species during anodizing of aluminium and AA2024-T3 alloy in sulphuric acid and tartaric-sulphuric acid (TSA) electrolytes. The investigation comprises four main parts; (i) Effects of fluoride on barrier film formation on aluminium. (ii) Effects of fluoride and fluorozirconic acid (FZ) on porous film growth on aluminium in sulphuric acid. (iii) Effects of FZ on porous film growth on aluminium and AA 2024-T3 alloy in sulphuric acid and TSA. (iv) Effects on anodizing of other fluoroacids (fluoroboric (FB), fluorosilicic (FS) and fluorotitanic acid (FT)). The anodic films were examined by analytical scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, Rutherford backscattering spectroscopy, nuclear reaction analysis and glow discharge optical emission spectroscopy. The behaviour of fluoride ions during the growth of barrier-type films on aluminium was investigated in ammonium pentaborate solution with added sodium fluoride. Additions of up to 3.5 x 10-3 M sodium fluoride had a negligible influence on the film growth. In contrast, 3.5 x 10-2 M sodium fluoride reduced the efficiency to 60% as fluoride ions promoted field-assisted ejection of Al3+ ions from the film. Incorporated fluoride ions migrated inwards at a rate about twice that of O2- ions, forming a fluoride-rich layer at the film base. The study of the influence of FZ on formation of porous anodic films in sulphuric acid and TSA employed a range of anodizing voltages, electrolyte temperatures and anodizing times. Fluoroacid increased the growth rate, with a reducing influence as the temperature increased. The films contained fluoride and sulphate ions, zirconium was not detected. The fluoride concentration decreased with increasing temperature, whereas the sulphate concentration was unaffected. Anodizing aluminium and AA 2024-T3 alloy in other fluoroacids resulted in similar influences on the anodizing behaviour as FZ. The differences in growth rate, film composition and film morphology were comparatively small and did not show a systematic dependence on the type of fluoroacid employed. Boron, silicon and titanium were not detected in the films.
10
Curtis, Sean Allan. "The effects of shot peening on corrosion fatigue of aluminium alloy 2024 T351 and 7150 T651." Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289664.
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11
Petersen, Amanda de Moura. "Comportamento inibidor da corrosão de antocianinas na liga de alumínio 2024-T3." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/153271.
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A eficiência de antocianinas como inibidores de corrosão da liga de alumínio 2024-T3 foi avaliada através de medidas eletroquímicas como a espectroscopia de impedância eletroquímica e polarizações anódica e catódica. Soluções de NaCl 0,025 mol.L-1 contendo diferentes concentrações (800, 1000, 2000, 3000, 5000 e 7200 ppm) de antocianinas extraídas da uva foram preparadas para analisar o efeito da presença destas substâncias quando em contato com a liga de alumínio 2024-T3. Medidas de espectroscopia de impedância eletroquímica apresentaram uma diminuição sobre a dispersão dos pontos nas regiões de baixas frequências com o acréscimo do tempo de contato das antocianinas com a superfície da liga de alumínio 2024-T3 de 1 hora para 3 dias de imersão. Além disso, o comportamento indutivo nestas regiões decresceu após 3 dias de imersão com uma elevação considerável da resistência à polarização e da eficiência de inibição em 1000 ppm de antocianinas. Sob polarizações anódica e catódica, também foi verificado um melhoramento generalizado das propriedades anticorrosivas como potencial de corrosão, corrente de corrosão e eficiência de proteção contra a corrosão, para a concentração de 1000 ppm de antocianinas. Análises de microscopia eletrônica de varredura, microscopia de força atômica e espectroscopia por dispersão de energia, confirmam a adsorção de antocianinas na superfície da liga, assim como medidas de absorbância após 3 dias de imersão.The efficiency of anthocyanins as corrosion inhibitor of the 2024-T3 aluminum alloy was evaluated by electrochemical measurements such as electrochemical impedance spectroscopy and anodic and cathodic polarizations. NaCl solutions 0.025 mol.L-1 containing different concentrations (800, 1000, 2000, 3000, 5000 and 7200 ppm) of anthocyanins extracted from grape were prepared to examine the effect of the presence of these substances when in contact with the 2024-T3 aluminum alloy. Electrochemical impedance spectroscopy measurements showed a decrease on the dispersion of points in the lower frequency regions with an increase of contact time of anthocyanins with the surface of the 2024-T3 aluminum alloy from 1 hour to 3 days of immersion. In addition, the inductive behavior in these regions decreased after 3 days of immersion with a considerable increase of the polarization resistance and inhibition efficiency of 1000 ppm of anthocyanins. Under cathodic and anodic polarizations, it was noted a general improvement in the anticorrosive properties such as corrosion potential, corrosion current and efficiency of protection against corrosion for the concentration of 1000 ppm of anthocyanins. Analyses of scanning electron microscopy, atomic force microscopy and energy dispersive spectroscopy confirm anthocyanins adsorption on to the surface alloy, as well as absorbance measurements in a spectrophotometer after 3 days of immersion.
12
Roungos, Ioannis C. "The effect of sequential action of corrosion and fatigue on fatigue crack initiation and propagation in 2024-T3 aluminium alloy." Thesis, Cranfield University, 1997. http://dspace.lib.cranfield.ac.uk/handle/1826/11122.
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The influence of sequential action of corrosion and fatigue on fatigue behaviour of 2024- T3 aluminium alloy was investigated. EXCO solution was used for corrosion development. Corrosion evolution and penetration were investigated in terms of exposure time, dimensional characteristics, orientation, microstructure of material, incremental corrosion application and sequential application of corrosion and fatigue. Single Edge Notch Tensile specimens were used in the fatigue-corrosion tests. Fatigue intervals were interrupted by corrosion application. Four fatigue intervals and four corrosion segment times were incorporated in the test matrix. The results of fatigue ínitiation, propagation and total life were compared to the virgin and pre-corroded materials' behaviour. The main mechanisms of crack acceleration and arrest were identified and discussed relative to the morphology of corrosion development. Finally a comparison was tried between the experimental lives and the predicted ones, calculated from two crack growth packages using the most conservative approach.
13
Roungos, I. C. "The effect of sequential action of corrosion and fatigue on fatigue crack initiation and propagation in 2024-T3 aluminium alloy." Thesis, Cranfield University, 1997. http://dspace.lib.cranfield.ac.uk/handle/1826/11122.
Full textAbstract:
The influence of sequential action of corrosion and fatigue on fatigue behaviour of 2024-
T3 aluminium
alloy was investigated. EXCO solution was used for corrosion
development. Corrosion evolution and penetration were investigated in terms of
exposure time, dimensional characteristics, orientation, microstructure of material,
incremental corrosion
application and sequential application of corrosion and fatigue.
Single Edge Notch Tensile specimens were used in the fatigue-corrosion tests. Fatigue
intervals were
interrupted by corrosion application. Four fatigue intervals and four
corrosion
segment times were incorporated in the test matrix. The results of fatigue
ínitiation, propagation and total life were compared to the virgin and pre-corroded
materials' behaviour. The main mechanisms of crack acceleration and arrest were
identified and discussed relative to the
morphology of corrosion development. Finally a
comparison was tried between the experimental lives and the predicted ones, calculated
from two crack
growth packages using the most conservative approach.
14
Amand, Sylvain. "Etude par spectroscopies d'impédance électrochimique globale et locale d'une monocouche hybride organique-inorganique respectueuse de l'environnement pour la protection contre la corrosion de l'alliage d'aluminium 2024." Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0025/document.
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L'utilisation de revêtements sol-gel pour la protection contre la corrosion des métaux est une alternative aux traitements à base de chromates, proscrits du fait de leur forte toxicité. Ces travaux de thèse ont porté sur la caractérisation de revêtements sol-gel hybrides organique-inorganique contenant des pigments inhibiteurs de corrosion non toxiques, pour la protection contre la corrosion de l'alliage d'aluminium 2024. Tout d'abord, la caractérisation par spectroscopie d'impédance électrochimique de différents revêtements relativement poreux a permis d'analyser l'influence de l'épaisseur, de la température de séchage, de l'hydrolyse de la partie silane et du ratio silane/amine sur les performances du revêtement, en particulier des propriétés barrière. Puis, l'ajout d'un époxy dans la formulation a permis d'augmenter de façon significative les propriétés barrière du film. Les diagrammes d'impédance présentent une dispersion en fréquence, exprimée en termes de « constant phase element (CPE) », en haute et basse fréquence. En haute fréquence, ce comportement a été analysé à l'aide d'un modèle qui permet d'obtenir des profils de résistivité dans l'épaisseur du revêtement et au cours du temps d'immersion. Ce modèle est appliqué pour la première fois à l'étude de revêtements. Différents pigments inhibiteurs de corrosion ont ensuite été incorporés dans des revêtements de porosité différente. L'action des inhibiteurs est exacerbée lorsqu'ils sont incorporés dans un revêtement poreux. Néanmoins, lorsqu'ils sont incorporés dans un film dense, les performances vis-à-vis de la résistance à la corrosion sont élevéesThe use of sol-gel coatings for the protection against the corrosion of metals is an alternative to chrome-based treatments, banned for the industry for their high toxicity. This work is based on the characterisation of hybrid organic-inorganic coatings, filled with non-toxic corrosion inhibitors, for the protection against the corrosion of aluminium alloy 2024. First, the characterisation by electrochemical impedance spectroscopy of different, relatively porous coatings, allowed the investigation of the influence of thickness, drying temperature, silane hydrolysis, and the silane/amine ratio on the coating performances, in particular the barrier properties. Then, the addition of an epoxy compound in the formulation allowed a significant increase in the film barrier properties. The impedance diagrams show a frequency dispersion, expressed in terms of a constant phase element (CPE), both in the high and low frequency range. In the high frequency range, this behaviour was analyzed using a model that allows obtaining resistivity profiles in the thickness of the coating and with immersion time. This model is applied for the first time to study coatings. Different corrosion inhibitors were then incorporated in coatings of different porosity. The action of the inhibitors was heightened when they are incorporated in a porous coating. Nevertheless, in a dense coating, the performances towards corrosion are high
15
Tan, Jeffrey Meng-Lee. "Residual stress and fatigue crack growth life prediction in fastener holes cold-worked by uniform indentation in 2024-T351 aluminium alloy." Thesis, Open University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500610.
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This thesis concerns primarily the residual stress characterisation in fastener holes cold worked by a novel StressWave process, and the prediction of the fatigue crack growth under the influence of such residual stress. Aerospace 2024-T351 aluminium alloy plate of 6.35mm thickness containing a nominal 06.35mm hole was used. Using neutron and laboratory X-ray diffraction measurements, a large compressive residual stress was found in StressWave and split-sleeve cold-worked holes. Detailed stress mapping indicates that a StressWave hole contains a highly symmetric residual stress field with a wider compression region. Conversely, the spht-sleeve technique generates a complex asymmetric stress variation through the specimen thickness and around the hole. Independently, a comprehensive finite element study was conducted to reveal the residual stess development associated with two distinct cold-working techniques at various stages. Favourable agreement was achieved between the experiment and simulations. The deformation mechanism associated with the cold-working process is decisive to the behaviour of the residual stress field created. The symmetric crack growth behaviour observed-in StressWave specimens permits a through-thickness crack geometry to be considered. Accordingly, Green's functions for a single crack and two symmetric cracks originating from the edge of a circular hole were developed. These solutions were verified using weight function and finite element analysis and are therefore appropriate for subsequent study of fatigue crack growth. A theoretical framework was proposed to explicate the interaction of residual stress with the superimposed loading at the crack tip, which was mathematically expounded as a function of stress intensity factor and stress ratio. This analytical framework provides a reasonable correlation between the mean stress and crack closure criteria.
16
Stimpfling, Thomas. "Modified layered double hydroxide (LDH) platelets as corrosion inhibitors reservoirs dispersed into coating for aluminun alloy 2024." Thesis, Clermont-Ferrand 2, 2011. http://www.theses.fr/2011CLF22169.
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L’alliage d’aluminium 2024 est très répandu dans l’industrie aéronautique et automobile. Le processus de corrosion peut entrainer des dommages irréversibles pouvant engendrer des issues fatales dans le domaine aéronautique. Ainsi plusieurs couches de revêtements sont déposées à la surface du métal à protéger pour prévenir le processus de corrosion. Depuis le début du 20ième siècle, le chrome hexavalent (CrVI) a été largement utilisé comme inhibiteur de corrosion dans les différentes couches du revêtement (prétraitement, primer et top-coat). La toxicité de ce composé envers l’homme et l’environnement a entrainé son interdiction et donc son remplacement comme agent de protection. Le confinement d’agent anticorrosif dans des nano-conteneurs a ainsi été reporté puisqu’un effet auto-réparant, en relargant sur demande, peut-être apporté : l’inhibiteur de corrosion agit quand le dommage apparait. Cette étude est focalisée sur l’utilisation de matériaux de type Hydroxydes Doubles Lamellaires (HDL) comme réservoir d’inhibiteurs de corrosion en raison leur propriété d’échange. Dans ce travail, plusieurs molécules ont été étudiées comme potentiel inhibiteur de corrosion. Celles-ci ont été tout d’abord caractérisées par DC-polarisation afin de déterminer la nature de leur comportement inhibiteur (anodique, cathodique ou les deux). Ensuite, ces agents anticorrosifs ont été intercalés dans des matrices HDL et leur capacité de relargage ainsi que leur comportement face au processus de corrosion ont été étudiés. Les particules HDL ainsi obtenues ont été dispersées dans la formulation d’un revêtement primaire et déposé directement sur l’alliage aluminium 2024. La résistance à la corrosion a été suivie par spectroscopie d’impédance complexe. Les propriétés d’auto-protection de notre revêtement (relargage d’agent anticorrosive encas de dommage) et leur propriété barrière, apportée par la morphologie lamellaire des nano-conteneurs, entrainant une diminution de la perméabilité aux espèces agressives (ex. eau, O2, électrolyte) responsable de l’apparition de cloques sur les revêtements, ont ainsi été caractériséesAluminum alloy 2024 is widely used in aircraft and automotive industry. Corrosion processes can provide irreversible damage on the metal substrate which could have a tragic issue in the aircraft domain. Thus, several coating layers have been applied on the metal substrate to prevent corrosion process. Since the beginning of the 20th century, hexavalent chromate compounds have been extensively used as corrosion inhibitor agents for paint, primer and conversion coating. The toxicity for human health and environment has led to replace such compounds. The literature has reported different possibilities to replace such unfriendly compounds. Moreover, the entrapment of corrosion inhibitors in nanocontainer provides a self-healing effect by releasing, on demand, the active species when damage occurs. This study focuses on Layered Double Hydroxide (LDH) material as reservoir due to its exchange properties. This study has characterized several potential corrosion inhibitor molecules by DC-Polarization to determine the nature of the inhibitor compound (i.e. anodic, cathodic or both of them). Further, active anticorrosive species have been intercalated into LDH framework. Then, the release of inhibitor agents and their subsequent behaviour toward corrosion inhibition have been evaluated. Modified LDH materials have been further dispersed in the primer coating formulation and applied on aluminum alloys 2024 substrate. Corrosion inhibition has been followed by electrochemical impedance spectroscopy experiments on scratched and unscratched panel which have permitted to evaluate the self-healing property of these modified LDH materials when damage occurs and the barrier property provided by the lamellar morphology of the inorganic reservoir that is found to decrease the permeation by enhancing the tortuosity of the coating layer towards aggressive species (i.e. water, O2, electrolyte) responsible of the blistering phenomenon
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Verdalet-Guardiola, Xavier. "Réactivité dans les bains de prétraitement et mécanismes de croissance des couches de conversion au chrome trivalent sur un alliage d'aluminium 2024." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30023.
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Composants principaux des couches de conversion chimique sur le marché, les composés à base de chrome hexavalent vont être interdits par la réglementation européenne REACh à partir de l'année 2024. Depuis plusieurs années, les industriels du secteur aéronautique développent donc des solutions de substitution basées sur le chrome trivalent, moins toxique et moins néfaste pour l'environnement que le chrome hexavalent, tout en conférant des propriétés anticorrosion prometteuses aux alliages d'aluminium. Le déploiement des solutions de conversion chimique à base de CrIII à l'échelle industrielle a mis en évidence une sensibilité forte de ces procédés aux propriétés de surface des alliages d'aluminium. Ce projet de thèse vise à améliorer la robustesse du procédé de conversion au chrome trivalent en identifiant les paramètres de premier ordre contrôlant les performances anticorrosion des couches. Pour cela, des éléments de compréhension concernant les modifications de surface causées par la préparation de surface et les mécanismes de croissance de la couche ont été apportés. Les travaux de thèse ont été réalisés sur l'alliage d'aluminium 2024 largement employé dans le domaine aéronautique. Différents lots d'alliage, états de surface et états métallurgiques ont été considérés afin de déterminer l'impact de la métallurgie de l'alliage sur les propriétés de surface après préparation de surface ainsi que sur les propriétés anticorrosion de la couche formée. L'étude de la réactivité de l'alliage dans le bain de conversion chimique a ensuite permis de mettre en évidence les mécanismes de nucléation et croissance de la couche de conversion. Un modèle de formation de la couche en surface de l'alliage 2024-T3 a ainsi été proposéHexavalent chromium, one of the main components of the chemical conversion coatings on the market, will be banned by European REACh regulations from 2024. From several years, manufacturers in the aeronautical sector have been developing substitution solutions based on trivalent chromium. These solutions with promising anti-corrosion properties as compared to hexavalent chromium are less toxic and less harmful to the environment than hexavalent chromium. However, the deployment of the CrIII conversion coatings to the industrial scale highlighted a higher sensitivity of these processes, as compared to the CrVI solutions, to the surface properties of the aluminium alloys. This work aims at improving the robustness of the trivalent chromium conversion process of the aluminium alloys by identifying the first order parameters controlling the anticorrosion performances of the conversion coatings. For that purpose, elements of understanding concerning the surface modifications caused by the surface preparation as well as data on the mechanisms of growth of the coating were brought. The thesis work was carried out on aluminium alloy 2024, which is widely used in the aeronautical field. Various alloy batches, surface states and metallurgical states were considered in order to determine the impact of alloy metallurgy on the surface properties after surface preparation as well as on the anticorrosive properties of the coating. The study of the reactivity of the alloy in the chemical conversion bath gave relevant data on the mechanisms of nucleation and growth of the conversion layer. As a result, a model for the formation of the conversion coating for 2024-T3 alloy was proposed
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Billy, Fabien. "Vieillissement et propriétés résiduelles de matériaux issus du démantèlement d'avions en fin de vie." Phd thesis, ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2013. http://tel.archives-ouvertes.fr/tel-00824151.
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Cette thèse s'inscrit dans le cadre d'un vaste programme visant à établir un premier retour d'expérience sur des structures aéronautiques en fin de vie. L'objectif des travaux présentés ici est donc de caractériser le vieillissement et les propriétés résiduelles de pièces provenant d'avions après démantèlement, et donc après service. Plus précisément, deux matériaux de nature différente sont considérés : un alliage d'aluminium 2024-T351, constitutif d'une voilure d'A320 ; et un composite carbone/époxy T300/914, prélevé sur les voilures d'un Falcon X et d'un ATR.Pour les voilures composites, les travaux ont porté sur les effets de l'eau des stratifiés. L'évolution de la température de transition vitreuse en DMA a été étudiée en fonction du taux d'humidité présente dans le stratifié. Les résultats d'essais de sorption set de désorption ont été confrontés à différents modèles de diffusion. Les propriétés résiduelles ont été évaluée au travers de divers essais mécaniques. Il ressort de cette étude un très bon comportement du composite après service.Les travaux concernant la voilure métallique se focalisent sur les propriétés résiduelles en fatigue de l'alliage de voilure. Les résultats montrent qu'un durcissement structural apparaît en service, et qu'un léger abattement de la durée de vie en fatigue est observable. Cependant, le comportement à la fissuration est inchangé en comparaison avec un matériau " neuf ".Au final, ce premier retour d'expérience est positif. Il peut maintenant permettre aux avionneurs de vérifier les règles utilisées lors de la conception ou d'optimiser certains dimensionnements, mais aussi de justifier des extensions de durée de vie des avions.
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Judas, Jakub. "Extrémně nízkocyklová únavová životnost slitin neželezných kovů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-400859.
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This thesis is focused on fatigue behaviour of aluminium alloy 2024-T351 in low cycle and extremely low cycle fatigue regime. Test specimens were firstly subjected to quasi-static tensile and compression tests to establish basic mechanical properties of the experimental material. Fatigue tests were conducted in strain-control mode, when cyclic plastic response and S-N curves were determined. All of the experiments were conducted at room temperature. Shapes of mechanical hysteresis loops are dependent on the strain amplitude and clearly exhibit cyclic plasticity of the alloy. Cyclic deformation curve was fitted by power regression function and subsequently compared with the tensile test. Experimental data of the S-N curves were fitted by Manson-Coffin and Wöhler-Basquin law. The discrepancy of the fatigue data was observed in the extremely low cycle fatigue regime. Based on this phenomenon, new regression function was used to overcome shortening of fatigue life in the extremely low cycle regime.
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Bonzom, Rémy. "Mesure des cinétiques de propagation de la corrosion intergranulaire de l’alliage d’aluminium 2024 : nouvelles approches expérimentales de l’endommagement en fonction des conditions environnementales." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCK048/document.
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Le coût de la maintenance aéronautique pourrait être réduit en proposant des stratégies d’inspection « intelligentes » intégrant des outils prédictifs de l’évolution des défauts, comme la vitesse de propagation de la corrosion intergranulaire.Dans cette thèse, nous avons cherché à quantifier les deux modes d’endommagement associés à la corrosion intergranulaire sur un alliage 2024 : la composante « perforante » (dissolution des pointes de joint de grain) et la composante « émoussante » (dissolution des parois des grains dans les cavités intergranulaires). Pour évaluer la composante « perforante », nous proposons une nouvelle variante de la méthode TFP (méthode OTFP) plus complète car elle ne se limite pas à caractériser le défaut le plus rapide mais permet de suivre l’ensemble des défauts perforants grâce à la nature optique de la détection. Dans cette méthode, le dispositif expérimental laisse libre la face de détection, ce qui permet de prélever l’électrolyte issu des cavités intergranulaires et de procéder à son analyse chimique. Cette donnée, peu connue à ce jour, a été utilisée pour valider des modèles de « transport réactif » qui pourront servir de base à des simulations prédictives intégrant l’effet de la nature de l’environnement. La porosité au sein du matériau induite par la corrosion intergranulaire et amplifiée par la dissolution « émoussante » a été suivie en temps réel par mesure de la conductivité électrique avec une sonde à courants de Foucault. D’abord calibrées en régime potentiostatique, ces méthodes se sont par la suite révélées efficaces pour évaluer l’endommagement associé à la corrosion intergranulaire lors d’une corrosion de type atmosphériqueCosts of aeronautical maintenance can be reduced by implementation of “smart” inspection strategies integrating predictive data on the evolution of defects such as the propagation rate of intergranular corrosion.In this work, intergranular corrosion damage on 2024 aluminium alloy was characterized by two modes : the “perforating” damage (dissolution of the grain boundary tips) and the “blunting” damage (dissolution of the grain walls in the intergranular cavities). To evaluate the “perforating” damage, a new version of the TFP method (OTFP method) which is more complete, was designed. The OTFP method allows to detect all the intergranular corrosion defects and not only the fastest full penetrating grain boundary thanks to the optical nature of the detection. In this method the detection backside of the thin foil is free, which makes possible the collection of the trapped electrolyte in the intergranular cavities to carry out its chemical analysis. This not well-known data, was used to validate “mass-transport” models which could be implemented in predictive simulations considering the effect of the environmental conditions. The porosity inside the foil induced by the intergranular corrosion and enhanced by the “blunting” dissolution was followed in real-time by measuring the electrical conductivity using an eddy current probe.These methods were first calibrated in potentiostatic tests and then successfully applied to evaluate the intergranular corrosion damage in atmospheric corrosion conditions
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Le, Thi My Linh. "Simulation de l'effet du confinement sur l'endommagement d'un assemblage en alliage d'aluminium." Thesis, Dijon, 2013. http://www.theses.fr/2013DIJOS048.
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Pour les structures aéronautiques, les zones sensibles à la corrosion sont principalement celles où le plan de protection de la structure peut être mis en défaut, comme à l’intérieur des joints de recouvrement (dénommé «lap joint» en anglais). Les assemblages de tôles métalliques réalisés par recouvrement en utilisant, par exemple le rivetage, peuvent présenter des défauts de contact et donc il peut exister un interstice entre les deux parties de l’assemblage. En général cet interstice est isolé de l’environnement extérieur par un mastic. Mais il y a un risque de piégeage d’humidité plus ou moins concentrée en ions agressifs qui peut provoquer des endommagements ou aggraver ceux initiés sur des défauts des revêtements. Le premier objectif de cette thèse est de développer une méthodologie permettant de reproduire, de manière contrôlée et de façon la plus représentative de cas réels, la corrosion d’un alliage d’aluminium 2024-T3 constituant un joint de recouvrement afin d’effectuer des observations complétées par des mesures chimiques et électrochimiques. Le deuxième objectif est de tester l’application de modèles de transport réactif (en milieu confiné) pour voir s’il est possible de simuler les réponses (chimiques ou électrochimiques) mesurées expérimentalement et donc de prédire sur le long terme l’évolution d’un assemblageFor aircraft structures, corrosion sensitive areas are mainly those where the protection of the structure may suffer local breakdowns, as encountered inside lap joints. The assemblies of metal plates by overlapping (riveting) may present some defects in contact and consequently a gap can exist between the two parts of the assembly. Typically this gap is isolated from the outside environment by a sealant. But there is a risk of trapping of moisture more or less concentrated in aggressive ions which can induce corrosion or increase the damages initiated on coating defects. The first objective of this thesis is to develop a methodology to reproduce in a controlled manner and in the most representative way regarding actual cases, the corrosion of a lap joint made of aluminum alloy 2024- T3 plates, to perform not only observations but also chemical and electrochemical measurements. The second objective is to test the application of reactive transport models (in confined media) to check if it is possible to simulate the chemical or electrochemical changes recorded during experiments and thus to predict the long-term evolution of lap-joint in humid environment
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Even, Anaïs. "Compréhension des mécanismes d'inhibition de la corrosion dans le cadre de revêtements hybrides pour pièces aéronautiques." Thesis, Lorient, 2019. http://www.theses.fr/2019LORIS534.
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La lutte contre la corrosion dans l'industrie aéronautique est un défi permanent. Pour y répondre, le système actuel fait appel aux chromates qui présentent des qualités anticorrosives. Ces composés sont cependant classés cancérigènes, mutagènes, reprotoxiques. Un revêtement hybride sol-gel/polymère non toxique a été développé pour proposer une alternative au système de référence. Il présente des performances de protection contre la corrosion de l’alliage d’aluminium 2024-T3. Ce revêtement est innovant par son application par pulvérisation et sa polymérisation sous irradiation UV. Ce système est complexe et la compréhension des mécanismes mis en jeu lors de l’inhibition de la corrosion a fait l’objet de ce travail de thèse. Tout d'abord, les travaux menés ont permis de mettre en évidence la protection passive du revêtement et de relier ses performances à la structuration du film jusqu’à l’échelle nanométrique. Ensuite, en cas d’endommagement du revêtement, la protection active du revêtement a été étudiée. Lors de la sollicitation du revêtement, la réponse active du système inhibiteur de corrosion a été caractérisée par une exposition en milieu naturel et complétée par des essais accélérés de corrosion cyclique. Ce travail de recherche a montré que l’action d’un inhibiteur de corrosion est étroitement dépendante de la matrice dans laquelle il est intégré. La matrice du revêtement étudié est fermée et dense, conférant un effet barrière, mais réduisant la mobilité des espèces actives lorsque le substrat à protéger est mis à nu. Ces tests révèlent que le revêtement hybride apporte uneprotection supérieure par comparaison à une peinture commerciale non chromatéThe struggle against corrosion in the aeronautical industry is an ongoing challenge. To meet these requirements, the current system uses chromates with anticorrosive properties. However, these compounds are classified as carcinogenic, mutagenic, reprotoxic. A non-toxic sol-gel/polymer hybrid coating has been developed to provide an alternative to the reference system. This coating is innovative in its application by spray and a one-step UV-curing polymerization. This system is complex and the understanding of the mechanisms involved in corrosion inhibition has been the subject of this thesis work. First, work conducted has allowed to highlight the passive protection of the coating and link its performance to the film structuration down to the nanoscale. Then, in case of damage to the coating, the active protection of the coating was studied. During solicitation of the coating, the active response of the corrosion inhibitor system was characterized by exposure to natural environment, supplemented by accelerated cyclic corrosion tests. This research work has shown that the action of a corrosion inhibitor is closely dependent on the matrix in which it is integrated. The coating matrix is closed and dense, providing a barrier effect, but reducing the mobility of active species when the substrate to be protected is exposed. These tests have shown that the hybrid coating provides superior protection in comparison with a non-chromatedcommercial paint
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Cai, Hong. "Microbiologically influenced corrosion and titanate conversion coatings on aluminum alloy 2024-T3 /." View online ; access limited to URI, 2006. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3225314.
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Vasudevan, Satish. "AN INVESTIGATION OF QUASI-STATIC BEHAVIOR, HIGH CYCLE FATIGUE AND FINAL FRACTURE BEHAVIOR OFALUMINUM ALLOY 2024 AND ALUMINUM ALLOY 2219." Akron, OH : University of Akron, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1193668130.
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Thesis (M.S.)--University of Akron, Dept. of Mechanical Engineering, 2007."December, 2007." Title from electronic thesis title page (viewed 02/23/2008) Advisor, T. S. Srivatsan; Faculty readers, Craig Menzemer, Amit Prakash; Department Chair, Celal Batur; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Silva, José Wilson de Jesus [UNESP]. "Efeito dos oxi-ânions do grupo VIB sobre a corrosão aquosa das ligas Al(2024) e Al(7050) utilizadas na indústria aeronaútica." Universidade Estadual Paulista (UNESP), 2003. http://hdl.handle.net/11449/97122.
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silva_jwj_me_guara.pdf: 1820882 bytes, checksum: 7e96fbad2b277d2b628c44604b9cf46d (MD5)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Foram caracterizados os comportamentos eletroquímicos e avaliadas as resistências à corrosão das ligas aeronáuticas 2024-T351 e 7050-T7451 em soluções aquosas de cloreto contendo cromato, molibdato e tungstato. Foram realizados ensaios de corrosão não-eletroquímicos de imersão prolongada acompanhados de análise metalográfica de superfície por microscopia óptica e identificação dos produtos de corrosão por difratometria de raios-X. A análise quantitativa de superfícies das ligas após a imersão, indica que os pites formados têm áreas médias similares. Os pites são mais largos do que profundos e de geometria, predominantemente, cônica ou quase-cônica e irregular. Em todos os produtos de corrosão de cada liga foi encontrado hidróxido de alumínio, em suas diferentes formas cristalinas. Medidas de perda de dureza, como uma conseqüência da deterioração superficial, também foram determinadas. Além disso, ensaios eletroquímicos como medidas de potencial em circuito aberto, curvas de polarização e voltametria cíclica complementaram este estudo. Em meio aerado os resultados obtidos mediante medidas eletroquímicas são consistentes com aqueles obtidos nos ensaios de imersão, em particular o efeito do CrO42- e do MoO42-. O WO42- mostrou-se agressivo em períodos prolongados de imersão. Apesar dos ensaios revelarem uma redução parcial de MoO42- em ambas as ligas, o efeito desse oxi-ânion parece ser diferente sobre cada liga. Em meio desaerado as ligas apresentam passivação em todos os eletrólitos. A adição dos oxi-ânions não modificou significativamente o potencial de pite para a liga 7050, enquanto que para a liga 2024 ele foi deslocado levemente para valores mais positivos.
It has been characterized the electrochemical behavior and evaluated the 2024-T351 and 7050-T7451 aircraft alloys corrosion resistance in chloride aqueous solutions containing chromate, molybdate and tungstate. It has been carried out non-electrochemical long immersion corrosion testings accompanied by surface metalography analysis achieved by light microscopy and corrosion products identification by X-ray difratometry. Surfaces quantitative analysis upon the alloys after immersion, indicates that formed pits have similar average area. Pits are widther than deeper and own predominantly a conical or quasi-conical and irregular geometry. In all corrosion products of each alloy it has been found aluminum hydroxide in its different crystalline ways. Hardness loss measurements have also been determined. In addition, electrochemical testings such as open circuit potential measures, polarization curves and cyclical voltammetry have completed this study. In aerated means the obtained results before electrochemical mesurements are similar to those obtained in the immersion tests, in particular CrO42- and MoO42- effects. WO42- has been found to be aggressive in very long immersion period. Though tests display a MoO42- partial reduction in both alloys, this oxi-anion effect seems to be different upon each alloy. In de-aerated means alloys present passivation in all eletrolytes. Oxi-anion addition has not changed significantly pit potential for 7050 alloy, while for 2024 alloy it has been dislocated, slightly, for more positive values.
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Akhtar, Anisa Shera. "Surface science studies of conversion coatings on 2024-T3 aluminum alloy." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/1713.
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The research in this thesis aims to develop new mechanistic knowledge for coating processes at 2024-Al alloy surfaces, ultimately to aid the design of new protective coatings. Coatings formed by phosphating, chromating, and permanganating were characterized especially by scanning Auger microscopy (SAM), X-ray photoelectron spectroscopy, and scanning electron microscopy . The objective was to learn about growth (nm level) as a function of time for different coating baths, as well as a function of lateral position across the different surface microstructural regions, specifically on the μm-sized Al-Cu-Mg and Al-Cu-Fe-Mn particles which are embedded in the alloy matrix . The research characterizes coating thickness, composition, and morphology.
The thesis emphasizes learning about the effect of different additives in zinc phosphating baths . It was found that the Ni²⁺ additive has two main roles : first, the rate of increase in local solution pH is limited by the slower kinetics of reactions involving Ni²⁺ compared to Zn²⁺, leading to thinner zinc phosphate (ZPO) coatings when Ni²⁺ is present. Second, most Ni²⁺ deposition occurs during the later stages of the coating process in the form of nickel phosphate and a Ni-Al oxide in the coating pores on the alloy surface, increasing the corrosion resistance. Aluminum fluoride precipitates first during the initial stages of the coating process, followed by aluminum phosphate, zinc oxide, and finally ZPO.
When Ni²⁺ is present in the coating solution at 2000 ppm, ZnO predominates in the coating above the A-Cu-Fe-Mn particle while ZPO dominates on the rest of the surface. The Mn²⁺ additive gives a more even coating distribution (compared with Ni²⁺) across the whole surface. The Mn²⁺ -containing ZPO coating is similar to the chromate coating in terms of evenness, while there is more coating deposition at the second-phase particles for permanganate coatings. The oxides on the Al-Cu-Fe-Mn and matrix regions are similar before coating, thereby confirming that a variety of observed differences in ZPO coating characteristics at these regions arise from the different electrochemical characteristics of the underlying metals. Upon exposure to a corrosive solution, the ZPO coating provides more protection to the second-phase particles compared to the matrix.
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Wang, Xi. "Corrosion Protection of Aluminum Alloy 2024-T3 by Al-Rich Primer." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1557143060015145.
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Gujarathi, Kedar Kanayalal. "Corrosion of aluminum alloy 2024 belonging to the 1930s in seawater environment." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3002.
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GUO, YANG. "A Study of Trivalent Chrome Process Coatings on Aluminum Alloy 2024-T3." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1308166499.
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Patel, Rishikumar M. "Investigating the Mechanical Behavior of Conventionally Processed High Strength Aluminum Alloy 2024." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1523106869575194.
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Silva, José Wilson de Jesus. "Efeito dos oxi-ânions do grupo VIB sobre a corrosão aquosa das ligas Al(2024) e Al(7050) utilizadas na indústria aeronaútica /." Guaratinguetá : [s.n.], 2003. http://hdl.handle.net/11449/97122.
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Resumo: Foram caracterizados os comportamentos eletroquímicos e avaliadas as resistências à corrosão das ligas aeronáuticas 2024-T351 e 7050-T7451 em soluções aquosas de cloreto contendo cromato, molibdato e tungstato. Foram realizados ensaios de corrosão não-eletroquímicos de imersão prolongada acompanhados de análise metalográfica de superfície por microscopia óptica e identificação dos produtos de corrosão por difratometria de raios-X. A análise quantitativa de superfícies das ligas após a imersão, indica que os pites formados têm áreas médias similares. Os pites são mais largos do que profundos e de geometria, predominantemente, cônica ou quase-cônica e irregular. Em todos os produtos de corrosão de cada liga foi encontrado hidróxido de alumínio, em suas diferentes formas cristalinas. Medidas de perda de dureza, como uma conseqüência da deterioração superficial, também foram determinadas. Além disso, ensaios eletroquímicos como medidas de potencial em circuito aberto, curvas de polarização e voltametria cíclica complementaram este estudo. Em meio aerado os resultados obtidos mediante medidas eletroquímicas são consistentes com aqueles obtidos nos ensaios de imersão, em particular o efeito do CrO42- e do MoO42-. O WO42- mostrou-se agressivo em períodos prolongados de imersão. Apesar dos ensaios revelarem uma redução parcial de MoO42- em ambas as ligas, o efeito desse oxi-ânion parece ser diferente sobre cada liga. Em meio desaerado as ligas apresentam passivação em todos os eletrólitos. A adição dos oxi-ânions não modificou significativamente o potencial de pite para a liga 7050, enquanto que para a liga 2024 ele foi deslocado levemente para valores mais positivos.Abstract: It has been characterized the electrochemical behavior and evaluated the 2024-T351 and 7050-T7451 aircraft alloys corrosion resistance in chloride aqueous solutions containing chromate, molybdate and tungstate. It has been carried out non-electrochemical long immersion corrosion testings accompanied by surface metalography analysis achieved by light microscopy and corrosion products identification by X-ray difratometry. Surfaces quantitative analysis upon the alloys after immersion, indicates that formed pits have similar average area. Pits are widther than deeper and own predominantly a conical or quasi-conical and irregular geometry. In all corrosion products of each alloy it has been found aluminum hydroxide in its different crystalline ways. Hardness loss measurements have also been determined. In addition, electrochemical testings such as open circuit potential measures, polarization curves and cyclical voltammetry have completed this study. In aerated means the obtained results before electrochemical mesurements are similar to those obtained in the immersion tests, in particular CrO42- and MoO42- effects. WO42- has been found to be aggressive in very long immersion period. Though tests display a MoO42- partial reduction in both alloys, this oxi-anion effect seems to be different upon each alloy. In de-aerated means alloys present passivation in all eletrolytes. Oxi-anion addition has not changed significantly pit potential for 7050 alloy, while for 2024 alloy it has been dislocated, slightly, for more positive values.
Orientador: Eduardo Norberto Codaro
Coorientador: Roberto Zenhei Nakazato
Banca: Luis Rogerio de Oliveira Hein
Banca: Gilberto Luis Jardim Pinto da Silva
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Mann, Philip. "Evaluation of surface modifications introduced by shot peening of aluminum alloy 2024-T351." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123117.
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Shot peening is a cold working mechanical deformation process consisting of bombarding a metallic surface with small spherical media, called shots, at velocities commonly in the range of 10 to 100 m/s. Upon impact, the shots generate a near-surface deformed layer containing local hardening as well as compressive residual stresses, resulting in an improved fatigue resistance. However, the dependence of shot velocity and percentage of the total area covered by shot impacts on the surface modification introduced by shot peening are not well understood.The hardness and residual stress profiles beneath shot peened surfaces were investigated using nanoindentation experiments for the situations of three different average shot velocities, corresponding to 35 m/s, 54 m/s and 66 m/s, and two surface coverages, corresponding to a single shot peening impingement and full coverage (100%). For the situation (i) of a single impingement, a new polishing procedure was developed allowing locating an isolated single impingement, verifying that the impingement was produced by a shot that impacted at normal incidence, as well as preparing the surface such that nanoindentation could be performed on the impingement's cross-section. It was demonstrated that both hardness and compressive residual stresses increased with an increase in shot velocity. The experimental residual stress results were compared to those from numerical simulations that utilized the same peening parameters as the experiments. It was observed that the experimental results demonstrated similar behavior and were of the same order of magnitude as those predicted numerically. The main difference was that the experimental results demonstrated a maximum compressive residual stress that was independent of shot velocity.For the situation (ii) of full coverage, channelling contrast imaging in a scanning electron microscope revealed that there were recrystallized grains adjacent to the shot peened edge. Additionally, the hardness and compressive residual stresses were observed to increase with an increase in shot velocity. Similarly to the single impingement, the location of maximum compressive residual stress was independent of shot velocity.Le grenaillage est un procédé de déformation mécanique consistant à bombarder une surface métallique ductile avec de petits billes sphériques à des vitesses élevées (10 à 100 m/s). Lors de l'impact, les billes génèrent l'apparition d'une zone déformée en surface, caractérisée par un durcissement relativement important ainsi qu'un champ de contraintes résiduelles de compression, ce qui entraîne une meilleure résistance à la fatigue. Cependant, l'effet de la vitesse d'impact de la bille et de la couverture de surface sur la modification des propriétés de surface induit par le grenaillage ne sont pas bien compris.Dans cette étude, la dureté et les contraintes résiduelles ont été étudiées en utilisant des expériences de nanoindentation pour les situations suivantes: trois vitesses de billes différentes correspondant à 35 m/s, 54 m/s et 66 m/s, ainsi que deux couvertures de surface correspondant à un seul impact et à une couverture complète (100%). Pour la situation (i) de l'étude d'un unique impact, une nouvelle procédure de polissage a été développée permettant de localiser un impact isolé. Cette procédure permet de préparer la surface de telle sorte que la nanoindentation peut être effectuée sur la section transversale de l'impact et permet de vérifier que l'impact a été produit par une bille frappant la surface avec une incidence normale. Il a été observé que la dureté et les contraintes résiduelles de compression augmentent avec une augmentation de la vitesse de la bille. Les résultats expérimentaux de contraintes résiduelles ont été comparés à ceux d'une simulation numérique en utilisant les mêmes paramètres expérimentaux de grenaillages. Il a été observé que les résultats expérimentaux montrent un comportement similaire et sont du même ordre de grandeur que ceux obtenus par simulation numérique. La principale différence est que les résultats expérimentaux ont montré une contrainte résiduelle de compression maximale étant indépendante de la vitesse de la bille.Pour la situation (ii) d'une couverture complète et à l'aide du procédé de microscopie électronique à balayage, nous avons observé un raffinement des grains adjacents à la surface grenaillée. En outre, nous avons observé que la dureté et les contraintes résiduelles de compression augmentaient avec une augmentation de la vitesse de la bille. De même que pour l'impact isolé, la localisation des contraintes résiduelles de compression maximale était indépendante de la vitesse de la bille.
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Lopez-Garrity, Omar A. "Corrosion Inhibition Mechanisms of Aluminum Alloy 2024-T3 by Selected non-Chromate Inhibitors." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1372077968.
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Costa, Douglas Henrique da Silva [UNESP]. "Estudo do efeito do processo de shot peening na taxa de propagação de trinca por fadiga na liga aeronáutica 2024 - T3." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/123234.
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000824425.pdf: 5119036 bytes, checksum: d2208b40c21a089b314a4455cfc48518 (MD5)Este trabalho tem por finalidade avaliar o efeito do processo de shot peening na taxa de propagação de uma trinca por fadiga já existente. O shot peening é um processo de trabalho a frio, que consiste no jateamento repetitivo com microesferas de aço, cerâmica ou vidro, na superfície de uma peça, produzindo encruamento e induzindo tensões residuais compressivas nas superfícies tratadas. Devido a isso, o shot peening tem-se mostrado um método bastante eficiente para dificultar o início e a propagação de uma trinca por fadiga a partir da superfície do material, melhorando a sua resistência à fadiga. Contudo, estudos de seu efeito sobre uma trinca já existente são pouco conhecidos. Corpos de prova do tipo CT, para a liga aeronáutica de alumínio 2024 - T3, foram inicialmente trincados por fadiga e, em seguida, submetidos ao processo de shot peening em ambos os lados. Após o tratamento, os ensaios foram reiniciados nas mesmas condições. Os ensaios foram realizados com amplitude constante em duas espessuras de corpos de prova e duas razões de carga, R, para analisar possíveis efeitos do estado de tensão na ponta da trinca nos resultados. Duas intensidades de shot peening foram utilizadas para cada valor de R ou espessura analisada. Também foram estudadas duas regiões de aplicação do processo de shot peening (atrás e em volta da ponta da trinca) em dois tamanhos de trincas. Curvas comparativas do comportamento da taxa de propagação de trincas por fadiga, mostrando a influência de cada um dos parâmetros descritos, são apresentadas, e suas diferenças, discutidas. Os resultados encontrados mostram que o processo de shot peening, quando realizado em um tamanho de trinca em pleno estágio II de propagação, apresenta maior influência quando aplicado atrás da ponta da trinca, com menor intensidade, em corpos de prova em estado ... (Resumo Completo, clicar acesso eletrônico abaixo)
This work focuses to evaluate the effect of the shot peening process in the propagation rate of a fatigue crack already existing. The shot peening is a cold working process, which consists of repetitive blasting with steel shot, ceramic or glass, the surface of a workpiece, producing hardening and inducing compressive residual stresses on the treated surfaces. Because of this, shot peening has proved a very efficient method for hindering the initiation and propagation of a fatigue crack from the surface of the material, improving its fatigue strength. However, studies of its effect on an already existing crack are little known. Specimens of type CT to the aeronautics aluminum alloy 2024 - T3, were initially cracked by fatigue and then subjected to shot peening process on both sides. After treatment, the tests were resumed under the same conditions. Tests were carried out with constant amplitude in two thicknesses of specimens and two load ratios, R, to analyze possible effects of stress state on the crack tip results. Two shot peening intensities were used for each R value or thicknesses analyzed, and were also studied two application regions of shot peening process (behind and around the crack tip) in two sizes of cracks. Comparative curves of the fatigue crack propagation rate, showing the influence of each of the parameters described are shown, and their differences discussed. The results show that the shot peening process, when performed in a crack size in full stage II propagation, has greater influence when applied behind the crack tip, with lower intensity, in the specimens in plane stress state and lower load ratio. For crack lower (close to the stage I of propagation), the shot peening process applied behind the crack tip induced delay in their propagation rate in all conditions studied. The delay effect on fatigue crack propagation rate ... (Complete abstract click electronic access below)
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Chilukuri, Anusha. "Corrosion Inhibition by Inorganic Cationic Inhibitors on the High Strength Aluminum Alloy, 2024-T3." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343784869.
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Gordon, Matthew. "A Nacreous Self-Assembled Nanolaminate for Corrosion Resistance on 2024-Al Alloy." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/33548.
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Nanometer thick layers of clay and polymer were formed on mica, silicon, and aluminum 2024-T3 alloy using alternating solutions of positively and negatively charged polymer and clay, respectively. Atomic force microscopy was used to observe the morphology of the composite films on mica and silicon. It was found that solution concentrations of clay above 0.02 weight percent lead to the uncontrolled deposition of clay platelets on the substrateâ s surface. By using solution concentrations of clay above 0.02 weight percent and ultrasonic agitation together it is possible to deposit a uniform monolayer of clay platelets on a mica substrate in £ 20 seconds. Ultrasonic agitation also produced crude patterns of montmorillonite platelets.
Thin films of poly(diallydimethylammonium chloride) (PDDA) were made using concentrations ³ 2 weight percent of PDDA. It was found that the PDDA formed several unusual morphologies. Spherulites of PDDA were observed with AFM and the glass transition temperature of high molecular weight PDDA was measured using differential scanning calorimetry (DSC).
Circular regions of positive charge were discovered on silicon wafers provided by three different sources. These areas of charge have never been reported in literature, but can easily be detected by placing wafers into solutions containing negatively or positively charged solutions of clay or polymer, respectively. The exact nature of these charged regions is unknown, but it is hypothesized that impurities on silicon wafers create the circular regions of positive charge.
ISAM films made of a polyamide salt and a synthetic clay, Laponite RD®, demonstrated significant corrosion resistance on 2024-T3 Al alloys after 168 hours of salt spray testing. The ISAM films offered corrosion protection only if there was a significant layer of underlying surface oxide present, however. It was found that ISAM deposited films of polyarylic acid (PAA) and polyallylamine hydrochloride (PAH) may offer some corrosion resistance on 2024-T3 Al alloys, but these filmsâ corrosion resistance is severely hampered by the presence of Cl- in the PAH solution.
Funding from this project was gratefully received from the Materials Science and Engineering Department at Virginia Tech; Luna Innovations Inc; the American Chemical Society / Petroleum Research Fund #34412-G5 and the Environmental Protection Agency Contract #68-D-00-244.Master of Science
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Gavelius, Marianne, and Karin Andersson. "Surface Treatment for Additive Manufactured Aluminum Alloys." Thesis, Linköpings universitet, Molekylär ytfysik och nanovetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-169027.
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Manufacturing of aircraft parts is often complex and time-consuming, which has led to an increased interest in new manufacturing technologies in the Swedish industry such as additive manufacturing (AM). Additive manufacturing techniques could be a solution to meet the aircrafts’ demand since it contributes to an efficient manufacturing and allows a just-in-time production of complex metal parts in their final shape. However, the use of AM aluminum for aircraft applications is in a development phase and no surface treatment process exists. Thereby, it is of high interest to further investigate surface treatments for AM alloys. Currently at Saab AB, conventional aluminum alloys are generally anodized in tartaric sulphuric acid (TSA) to improve the corrosion resistance and adhesion properties of the metal. On the behalf of Saab AB, there is also an interest in establishing powder coating as a surface treatment. This master thesis’ purpose is to investigate the anodizing and adhesion properties for the two additive manufacturing alloys - AlSi10Mg and ScalmalloyⓇ, and compare it with the conventionally produced Al alloy 2024-T3. The anodization and the powder coating is examined by using following characterization techniques: profilometry, light microscopy, scanning electron microscopy and contact angle measurements. The results from the experimental part indicated successful anodizations for all the alloys and good adhesion properties for powder coating. This research is a first step in contributing to a better understanding of the anodic coating and adhesion properties for the AM samples ScalmalloyⓇ and AlSi10Mg
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Zhao, Tianwen. "Fatigue of aluminum alloy 7075-T651 /." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3342620.
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Thesis (Ph. D.)--University of Nevada, Reno, 2008."December, 2008." Includes bibliographical references (leaves 76-83). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2009]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.
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ASHIRGADE, AKSHAY A. "ENVIRONMENTALLY-COMPLIANT NOVOLAC SUPERPRIMERS FOR CORROSION PROTECTION OF ALUMINUM ALLOYS." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1153245386.
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Boyle, Gavin James. "Influence of processing and structure on the superplastic properties of the aluminium alloy 2004." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409401.
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Saraloglu, Ebru. "Effect Of Ecap And Subsequent Heat Treatments On Microstructure And Mechanical Properties Of 2024 Aluminum Alloy." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609811/index.pdf.
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Severe plastic deformation (SPD) results in ultra-fine grain sizes in metals and alloys. Equal channel angular pressing (ECAP) is one of the special SPD methods aiming to introduce high plastic strains into the bulk materials without changing their cross section. ECAP results in improvement in hardness and strength while still satisfying acceptable ductility level. The combined effects of ECAP and subsequent heat treatments, i.e. post-aging and post-annealing, on the microstructure and hardness of the 2024 aluminum alloy were investigated. An ECAP die with 120˚
channel angle was constructed. Subgrain formation, increase in dislocation density and dislocation tangling were observed after ECAP, and subgrain growth was detected after post annealing. The specimens revealed higher hardness values after ECAP at room temperature, and further increase in hardness was observed following post-aging at 80&
#730
C, 100&
#730
C and 190&
#730
C. Effect of the aging temperature on the deformed specimens was investigated, and the aging behaviors of the severely deformed and undeformed samples at 190&
#730
C were compared.
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Mohin, Ma. "Fatigue crack growth assessment and fatigue resistance enhancement of aluminium alloys." Thesis, University of Hertfordshire, 2018. http://hdl.handle.net/2299/20824.
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Fatigue damage of aluminium alloys is one of the key concerns in transport industries, particularly in the aerospace industry. The purpose of the project is to develop new knowledge and techniques against fatigue failure for these industries through a systematic investigation of fatigue resistance and crack growth behaviours of aluminium alloys. Fatigue and fracture mechanics have been investigated analytically, numerically and experimentally in this project. Overload transient effect on fatigue crack growth has been examined by considering various parameters including crack closure, overload ratio (OLR), load ratio (R ratio), baseline stress intensity factor range, (∆K)_BL and geometry. It was found that crack closure can be correlated qualitatively and quantitatively to all other parameters associated with overload transient behaviour. It is proposed that the effect of crack tip plasticity on the non-linearity of the compliance curve can be separated to obtain reliable crack closure measurement. In this project, different methods are used to better understand the transient retardation process so that the damage tolerance design (DTD) of the components made of aluminium alloys can be enhanced. Another important parameter for fatigue and damage tolerance design (DTD) of engineering components is the threshold stress intensity factor range for fatigue crack growth, ∆K_th. A small variation in identification of ∆K_th can lead to a big change in overall estimation of fatigue life. In this project, an analytical model has been developed for aluminium alloys by fitting an analytical curve with raw crack growth data in order to identify the ∆K_th. This model has the capacity to identify ∆K_th for different aluminium alloys at various R ratios. There is a great demand for enhanced fatigue life of aluminium alloys in the transport industry. This project has carried out a detailed investigation of electromagnetic treatment (ET) in the form of electropulsing treatment to develop an efficient technique for fatigue resistance enhancement. ET parameters including the treatment intensity, treatment time and the number of applications have been optimised. It is suggested that the duration of ET treatment can be used as the main parameter among all these to control the fatigue resistance of the aluminium alloy. The improvement in fatigue resistance has been explained by the change in microhardness and conductivity of aluminium alloy due to ET. Additionally, the fracture morphology was analysed using scanning electron microscopy (SEM). The precipitates and dislocation characteristics were also studied using transmission electron microscopy (TEM). The outcomes of this investigation will help improve structural integrity by enhancing fatigue resistance of aluminium alloys.
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Costa, Douglas Henrique da Silva. "Estudo do efeito do processo de shot peening na taxa de propagação de trinca por fadiga na liga aeronáutica 2024 - T3 /." Guaratinguetá, 2015. http://hdl.handle.net/11449/123234.
Full textAbstract:
Orientador: Marcelo Augusto Santos TorresBanca: Antonio Jorge Abdalla
Banca: Carlos Antonio Reis Pereira Baptista
Resumo: Este trabalho tem por finalidade avaliar o efeito do processo de shot peening na taxa de propagação de uma trinca por fadiga já existente. O shot peening é um processo de trabalho a frio, que consiste no jateamento repetitivo com microesferas de aço, cerâmica ou vidro, na superfície de uma peça, produzindo encruamento e induzindo tensões residuais compressivas nas superfícies tratadas. Devido a isso, o shot peening tem-se mostrado um método bastante eficiente para dificultar o início e a propagação de uma trinca por fadiga a partir da superfície do material, melhorando a sua resistência à fadiga. Contudo, estudos de seu efeito sobre uma trinca já existente são pouco conhecidos. Corpos de prova do tipo CT, para a liga aeronáutica de alumínio 2024 - T3, foram inicialmente trincados por fadiga e, em seguida, submetidos ao processo de shot peening em ambos os lados. Após o tratamento, os ensaios foram reiniciados nas mesmas condições. Os ensaios foram realizados com amplitude constante em duas espessuras de corpos de prova e duas razões de carga, R, para analisar possíveis efeitos do estado de tensão na ponta da trinca nos resultados. Duas intensidades de shot peening foram utilizadas para cada valor de R ou espessura analisada. Também foram estudadas duas regiões de aplicação do processo de shot peening (atrás e em volta da ponta da trinca) em dois tamanhos de trincas. Curvas comparativas do comportamento da taxa de propagação de trincas por fadiga, mostrando a influência de cada um dos parâmetros descritos, são apresentadas, e suas diferenças, discutidas. Os resultados encontrados mostram que o processo de shot peening, quando realizado em um tamanho de trinca em pleno estágio II de propagação, apresenta maior influência quando aplicado atrás da ponta da trinca, com menor intensidade, em corpos de prova em estado ... (Resumo Completo, clicar acesso eletrônico abaixo)
Abstract: This work focuses to evaluate the effect of the shot peening process in the propagation rate of a fatigue crack already existing. The shot peening is a cold working process, which consists of repetitive blasting with steel shot, ceramic or glass, the surface of a workpiece, producing hardening and inducing compressive residual stresses on the treated surfaces. Because of this, shot peening has proved a very efficient method for hindering the initiation and propagation of a fatigue crack from the surface of the material, improving its fatigue strength. However, studies of its effect on an already existing crack are little known. Specimens of type CT to the aeronautics aluminum alloy 2024 - T3, were initially cracked by fatigue and then subjected to shot peening process on both sides. After treatment, the tests were resumed under the same conditions. Tests were carried out with constant amplitude in two thicknesses of specimens and two load ratios, R, to analyze possible effects of stress state on the crack tip results. Two shot peening intensities were used for each R value or thicknesses analyzed, and were also studied two application regions of shot peening process (behind and around the crack tip) in two sizes of cracks. Comparative curves of the fatigue crack propagation rate, showing the influence of each of the parameters described are shown, and their differences discussed. The results show that the shot peening process, when performed in a crack size in full stage II propagation, has greater influence when applied behind the crack tip, with lower intensity, in the specimens in plane stress state and lower load ratio. For crack lower (close to the stage I of propagation), the shot peening process applied behind the crack tip induced delay in their propagation rate in all conditions studied. The delay effect on fatigue crack propagation rate ... (Complete abstract click electronic access below)
Mestre
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Huang, I.-Wen Evan. "Uniform Corrosion and General Dissolution of Aluminum Alloys 2024-T3, 6061-T6, and 7075-T6." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469105977.
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Guo, Xiaolei. "Corrosion inhibition of aluminum alloy 2024-T3 based on smart coatings, hybrid corrosion inhibitors, and organic conversion coatings." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461188604.
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Tan, Evren. "Severe Plastic Deformation Of Age Hardenable Aluminum Alloys." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614968/index.pdf.
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Industrial products of high-strength Al-alloys are currently manufactured by thermo-mechanical processes, which are only applicable in the integrated plants requiring high investment cost. Moreover, reduction of the average grain size not less than 10 &mum and re-adjustment of process parameters for each alloy type is evaluated as disadvantage. Therefore, recently there have been many research studies for development of alternative manufacturing techniques for aluminum alloys. Research activities have shown that it is possible to improve the strength of Al-alloys remarkably by severe plastic deformation which results in ultra-fine grain size. This study aims to design and manufacture the laboratory scale set-ups for severe plastic deformation of aluminum alloys, and to characterize the severely deformed samples. The stages of the study are summarized below: First, for optimization of die design and investigation of parameters affecting the deformation finite element modeling simulations were performed. The effects of process parameters (die geometry, friction coefficient) and material properties (strain hardening, strain-rate sensitivity) were investigated. Next, Equal Channel Angular Pressing (ECAP) system that can severely deform the rod shaped samples were designed and manufactured. The variations in the microstructure and mechanical properties of 2024 Al-alloy rods deformed by ECAP were investigated. Finally, based on the experience gained, a Dissimilar Channel Angular Pressing (DCAP) system for severe plastic deformation of flat products was designed and manufactured
then, 6061 Al-alloy strips were deformed. By performing hardness and tension tests on the strips that were deformed by various passes, the capability of the DCAP set-up for production of ultra-fine grain sized high-strength aluminum flat samples were investigated.
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Nastic, Aleksandra. "Repair of Aluminum Alloy Aerospace Components and Cold Gas Dynamic Spray Flow Distribution Study." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32998.
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Aluminum alloys have been used for decades in aircraft as they offer a wide range of properties explicitly developed to provide a set of characteristics adapted to structural and non-structural components. However, aircraft components inevitably undergo degradation during service due to their extensive use and exposure to harsh environments. Typical repair methods are either not efficient for large scale repairs due to their low material growth rate, not suitable for field repair or involve the use of high process temperatures. The present research aims at evaluating the cold gas dynamic spray (CGDS) as a potential repair technology to restore Al7075-T6 nose landing gear steering actuator threads found on the Boeing 757 aircraft. Moreover, it studies the suitability of using cold spray to deposit Al2024 material. The influence of process parameters and substrate surface preparation on the material deposition efficiency and resulting microstructural and mechanical repair properties is also evaluated.
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Bonfils-Lahovary, Marie-Laëtitia de. "Endommagement en corrosion intergranulaire de l'alliage d'aluminium 2024 : mécanismes et cinétiques de propagation." Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/19319/7/BonfilsLahovary.pdf.
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La prédiction des durées de vie des pièces de structures aéronautiques a toujours été une problématique à la fois complexe et capitale dans ce domaine de l’industrie. Néanmoins, la majorité des tests existant à l’heure actuelle cherche à évaluer la capacité des matériaux à résister aux sollicitations mécaniques notamment en fatigue. Les problématiques liées à l’endommagement causé par l’environnement comme la corrosion sont encore mal comprises. En effet, bien que certains tests permettent de détecter et de caractériser cet endommagement, aucun outil fiable de prédiction des vitesses de propagation des défauts de corrosion intergranulaire n’existe. Ainsi, actuellement, un défaut de corrosion détecté induit systématiquement un changement de la pièce. Les travaux de cette thèse s’inscrivent dans cette problématique ; ils ont pour but de comprendre les phénomènes de corrosion intergranulaire sur l’alliage d’aluminium 2024, le plus utilisé dans le secteur aéronautique, et d’étudier les cinétiques de propagation des défauts de corrosion. L’étude s’appuie sur une approche multi-échelle des processus de corrosion, des états microstructuraux et de l’influence de l’hydrogène. Ce projet s’inscrit également dans une dynamique de collaboration avec Airbus Group et l’Université de Bourgogne dans le cadre du projet ANR M-SCOT (Multi-Scale Corrosion Testing ANR-14-CE07-0027-01).
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Widener, Christian Aragon Talia George E. "Evaluation of post-weld heat treatments for corrosion protection in friction stir welded 2024 and 7075 aluminum alloys." Diss., Click here for available full-text of this thesis, 2005. http://library.wichita.edu/digitallibrary/etd/2005/d004.pdf.
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Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering."December 2005." Title from PDF title page (viewed on February 8, 2007). Thesis adviser: George Talia. Includes bibliographic references leaves 192-203).
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André, Natália Manente. "Friction spot joining of aluminum alloy 2024-t3 and carbon-fiber-reinforced polyphenylene sulfide composite laminate with additional pps film interlayer." Universidade Federal de São Carlos, 2015. https://repositorio.ufscar.br/handle/ufscar/8275.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Friction Spot Joining (FSpJ) is a prize-winning joining technique for hybrid metal-polymer composite structures. This master thesis was devised to investigate the feasibility of FSpJ of metal-composite structures with additional film interlayer. Friction spot joints of aluminum alloy 2024-T3 and carbon-fiberreinforced polyphenylene sulfide laminate composite with additional PPS film interlayer were successfully produced. The highest peak temperature achieved during the joining process was 417°C. DSC analysis demonstrated that the degree of crystallinity decreased for the composite (from 22% to 12%) and increased for the PPS film (from 7% to 27%) after joining. TGA analysis indicated that no extensive thermo-mechanical degradation induced by the joining process occurred. The main bonding mechanisms of FSp joint were identified as macro- and micro-mechanical interlocking, as well as adhesion forces. The process-related microstructural effects were evaluated and correlated to the local mechanical performance of the joining parts through micro and nanohardness. Further, mechanical grinding, sandblasting and plasma activation surface pre-treatments were performed on the composite part to enhance the adhesion between the joining parts. The generated surface features due to the surface pre-treatments were correlated to the mechanical performance of the joints. Sandblasted specimens showed the best mechanical performance among the surface pre-treatments used in this work. The lap shear strength of joints with interlayer (2703 ± 114 N up to 3069 ± 166 N) was up to 55% higher than the corresponding joints without film. The fatigue life of the joints with interlayer was 4 times longer in comparison with those without interlayer; superior fatigue strength was also observed. The durability of the joints was evaluated through hydrothermal accelerated aging; the maximum reduction in initial strength was 12.4% for 28 days of aging. Finally, the failure mechanisms of the joints were discussed, demonstrating a mixture of adhesivecohesive failure mode.
A União Pontual por Fricção (FSpJ) é uma técnica internacionalmente premiada para união de estruturas híbridas metal-compósito polimérico. Esta dissertação de mestrado investigou a viabilidade técnica da produção de juntas metal-compósito com filme polimérico intermediário através do FSpJ. Juntas de alumínio 2024-T3 e laminado compósito de poli(sulfeto de fenileno) (PPS) reforçado com fibras de carbono com filme intermediário de PPS foram produzidas com sucesso. A máxima temperatura processual identificada foi de 417°C. Análises de DSC demonstraram decréscimo no grau de cristalinidade do compósito (de 22% para 12%) e acréscimo no caso do filme intermediário (de 7% para 27%) depois de submetidos ao processo de união. Análises de TGA não identificaram evidências de ocorrência de degradação termomecânica dos componentes poliméricos das juntas induzida pelo FSpJ. Os principais mecanismos de união identificados na interface das juntas foram macro- e micro-ancoramento mecânico, além de forças adesivas. As mudanças microestruturais induzidas pelo processo de união foram investigadas e correlacionadas com o desempenho mecânico local dos componentes da junta através de medidas de micro e nanodureza. Pré-tratamentos superficiais de lixamento, jateamento de areia e ativação por plasma foram realizados no componente compósito a fim de aprimorar a adesão entre os componentes a serem unidos. As superfícies pré-tratadas foram caracterizadas e suas propriedades foram correlacionadas com a resistência mecânica das juntas correspondentes. As amostras jateadas produziram juntas com a melhor resistência mecânica entre os pré-tratamentos superficiais investigados neste estudo. A resistência ao cisalhamento das juntas com filme (2703 ± 114 N até 3069 ± 166 N) apresentou-se até 55% superior à resistência das respectivas juntas sem filme. A vida em fadiga das juntas com filme apresentou-se cerca de 4 vezes mais longa em comparação às juntas sem filme. A durabilidade das juntas foi investigada através de envelhecimento hidrotérmico acelerado, sendo que a máxima redução em resistência ao cisalhamento foi de 12,4% para 28 dias de envelhecimento. Finalmente, os mecanismos de falha das juntas foram discutidos, demonstrando a predominância do modo coesivo de falha.