Microstructural Evolution in the 2219 Aluminum Alloy During Severe Plastic Deformation PDF Download
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Author:
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Languages : en
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Book Description
Numerous investigations have demonstrated that intense plastic deformation is an attractive procedure for producing an ultrafine grain size in metallic materials. Torsional deformation under high pressure and equal-channel angular extrusion are two techniques that can produce microstructures with grain sizes in the submicrometer and nanometer range. Materials with these microstructures have many attractive properties. The microstructures formed by these two processing techniques are essentially the same and thus the processes occurring during deformation should be the same. Most previous studies have examined the final microstructures produced as a result of severe plastic deformation and the resulting properties. Only a limited number of studies have examined the evolution of microstructure. As a result, some important aspects of ultra-fine grain formation during severe plastic deformation remain unknown. There is also limited data on the influence of the initial state of the material on the microstructural evolution and mechanisms of ultra-fine grain formation. This limited knowledge base makes optimization of processing routes difficult and retards commercial application of these techniques. The objective of the present work is to examine the microstructure evolution during severe plastic deformation of a 2219 aluminum alloy. Specific attention is given to the mechanism of ultrafine grain formation as a result of severe plastic deformation.
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Category :
Languages : en
Pages :
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Book Description
Numerous investigations have demonstrated that intense plastic deformation is an attractive procedure for producing an ultrafine grain size in metallic materials. Torsional deformation under high pressure and equal-channel angular extrusion are two techniques that can produce microstructures with grain sizes in the submicrometer and nanometer range. Materials with these microstructures have many attractive properties. The microstructures formed by these two processing techniques are essentially the same and thus the processes occurring during deformation should be the same. Most previous studies have examined the final microstructures produced as a result of severe plastic deformation and the resulting properties. Only a limited number of studies have examined the evolution of microstructure. As a result, some important aspects of ultra-fine grain formation during severe plastic deformation remain unknown. There is also limited data on the influence of the initial state of the material on the microstructural evolution and mechanisms of ultra-fine grain formation. This limited knowledge base makes optimization of processing routes difficult and retards commercial application of these techniques. The objective of the present work is to examine the microstructure evolution during severe plastic deformation of a 2219 aluminum alloy. Specific attention is given to the mechanism of ultrafine grain formation as a result of severe plastic deformation.
Author: Andrew Gilmore
Publisher:
ISBN:
Category : Aluminum alloys
Languages : en
Pages : 0
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This study comprehensively analyzed the mechanical behavior and microstructural evolution of aluminum alloy AA2219-T87 undergoing high deformation and strain rates at elevated temperature via hot torsion tests. An integrated experimental and modeling approach has been employed, where a finite element model is developed with ABAQUS to address local deformation and non-uniform temperature distribution along the specimen gauge section. A Johnson-Cook constitutive material model is calibrated based on the calculated and measured torque curves at different conditions. Combined with the ABAQUS calculated local thermo-mechanical conditions, microstructure modeling using established literature-based equations are established to provide insights into grain size distribution and recrystallization mechanisms. The calibrated material constitutive model, recrystallization model, and grain size model can be utilized to model various manufacturing processes which involves hot deformation of aluminum alloys in the intermediate strain rate range of 14/s-78/s. These findings were applied to further works with Bobbin Tool Friction Stir Welding of thick plate AA2219. Analysis of cross sections and welding parameter effects on microstructural and phenomenological outcomes were performed to maximize understanding of the specific material behavior in elevated temperature, high strain rate processes as seen in hot torsion as well as friction based solid state welding.
Author: Yogesh Bhambri
Publisher:
ISBN:
Category : Aluminum alloys
Languages : en
Pages : 130
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Author: Shelly Midori Miyasato
Publisher:
ISBN:
Category :
Languages : en
Pages : 312
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Author: Carlos D. Rincon
Publisher:
ISBN:
Category : Aluminum alloys
Languages : en
Pages : 222
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Author: Douglas L. Swisher
Publisher:
ISBN: 9781423532187
Category :
Languages : en
Pages : 82
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Equal channel-angular pressing (ECAP) is a recently developed method for deformation processing of material that can produce an ultra-fine grain structure in bulk material through severe plastic deformation. This study will present results on micro structural evolution during repetitive ECAP of pure aluminum. The principal method of data collection was Orientation Imaging Microscopy (OIM). The results of the study indicate that, after one ECAP pass, the structure is inhomogeneous and anisotropic, and consists mostly of deformation-induced features. After repetitive ECAP, the aluminum material exhibited a homogeneous grain size but retained an anisotropic character to the microstructure. After twelve ECAP passes the microstructure consisted mainly of fine grains surrounded by high-angle boundaries but an appreciable fraction of low-angle boundaries remained. This microstructure thus comprises a mixture of deformation-induced and recrystallization features. Further results were also obtained documenting the existence of deformation banding in this material as well as in a rolled aluminum alloy. This phenomenon may be general in nature and associated with severe plastic deformation in aluminum and its alloys.
Author: Samson Olusikunanu Odunuga
Publisher: ProQuest
ISBN: 9780549341284
Category :
Languages : en
Pages : 167
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The atomic transport resulting from plastic deformation has been analyzed in new depths by tracking the evolution of pair of marker atoms. This analysis has proved to be a powerful tool in identifying the deformation mechanisms, including the glide of leading and trailing partial dislocations, and vacancy assisted atomic jumps during deformation, as well as quantifying the relative contributions of these mechanisms. It is found that the glide of dislocations plays a more important role than previously thought in accommodating plastic deformation in nanocrystalline alloys. A new property of the atomic mixing by plastic deformation that has been uncovered is that the effective diffusion coefficient increases, nearly linearly, with the separation distance of pairs of atoms. This superdiffusive mixing is revealed by monitoring the relative displacement of atoms as a function of the separation distance. This result can be tested experimentally by measuring the rate of dissolution of precipitates during deformation. This finding also provides a direct rationalization for the stabilization of compositional patterns when thermal diffusion and forced mixing compete.
Author: Yuntian Theodore Zhu
Publisher: John Wiley & Sons
ISBN: 1118804481
Category : Technology & Engineering
Languages : en
Pages : 886
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Book Description
Proceedings of a symposium sponsored by the Shaping and Forming Committee of the Materials Processing and Manufacturing Division (MPMD) and the Mechanical Behavior Committee (Jt. SMD/ASM-MSCTS) of the Structural Materials Division (SMD) of TMS (The Minerals, Metals & Materials Society) and held during the 2002 TMS Annual Meeting in Seattle, Washington February 17-21,2002.
Author: Jing Lu
Publisher:
ISBN:
Category : Electronic thesis
Languages : en
Pages : 230
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 19
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A combined experimental and modeling study has been carried out to characterize the structure and mechanical properties of severely plastically deformed (SPD) aluminum and its alloys as well as the effect of strengthening mechanism on fracture toughness and failure mode. This investigation is focused specifically on Equal Channel Angular Pressing (ECAP) and heavy cold rolling of high solute Al alloys. A particular reason for studying the high strength potentially achievable by these routes is the expectation that since the fracture toughness of precipitation hardened aluminum alloys is known to be degraded by grain boundary precipitates, the high strengths achievable by strain hardening without precipitation has a reasonable prospect of yielding a higher combination of yield strength and toughness than by conventional precipitation hardening. In this study it has been shown that SPD processing of high solute Al alloys can be carried out to higher strains before strain localization occurs if mechanical stress relieving is done prior to processing and that strengths unobtainable through precipitation hardening can readily be achieved by strain hardening. The effect of natural aging on strain hardening has been investigated and found to be a significant factor in the rate at which the flow stress increases with increasing plastic strain. It has been shown that strain hardened Al alloys are more ductile and exhibit higher strain hardening rates then precipitation hardened alloys at equivalent strengths and that strain hardening is a viable processing route for improving toughness. On the modeling side, we have developed new micromechanical finite element models that employ crystal plasticity constitutive framework and are able to successfully simulate texture evolution in the sample during complex routes of ECAP.