Journal ArticleDOI
Superplasticity in powder metallurgy aluminum alloys and composites
TLDR
A detailed analysis of superplasticity in powder metallurgy aluminum alloys and composites has been reviewed through a detailed analysis as discussed by the authors, where the role of increasing misorientation of low angle boundaries to high angle boundaries by lattice dislocation absorption is examined.Abstract:
Superplasticity in powder metallurgy aluminum alloys and composites has been reviewed through a detailed analysis. The stress-strain curves can be put into four categories: a classical well-behaved type, continuous strain hardening type, continuous strain softening type and a complex type. The origin of these different types of stress-strain curves is discussed. The microstructural features of the processed material and the role of strain have been reviewed. The role of increasing misorientation of low angle boundaries to high angle boundaries by lattice dislocation absorption is examined. Threshold stresses have been determined and analyzed. The parametric dependencies for superplastic flow in modified conventional aluminum alloys, mechanically alloyed alloys and aluminum alloy matrix composites is determined to elucidate the superplastic mechanism at high strain rates. The role of incipient melting has been analyzed. A stress exponent of 2, an activation energy equal to that for grain boundary diffusion and a grain size dependence of 2 generally describes superplastic flow in modified conventional aluminum alloys and mechanically alloyed alloys. The present results agree well with the predictions of grain boundary sliding models. This suggests that the mechanism of high strain rate superplasticity in the above-mentioned alloys is similar to conventional superplasticity. The shift of optimum superplastic strain rates to higher values is a consequence of microstructural refinement. The parametric dependencies for superplasticity in aluminum alloy matrix composites, however, is different. A true activation energy of 313 kJ mol−1 best describes the composites having SiC reinforcements. The role of shape of the reinforcement (particle or whisker) and processing history is addressed. The analysis suggests that the mechanism for superplasticity in composites is interface diffusion controlled grain boundary sliding.read more
Citations
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Journal ArticleDOI
Bulk nanostructured materials from severe plastic deformation
TL;DR: In this article, the authors present methods of severe plastic deformation and formation of nanostructures, including Torsion straining under high pressure, ECA pressing, and multiple forging.
Book
Friction Stir Welding and Processing
Rajiv S. Mishra,Zongyi Ma +1 more
TL;DR: Friction stir welding (FSW) is a relatively new solid-state joining process that is used to join high-strength aerospace aluminum alloys and other metallic alloys that are hard to weld by conventional fusion welding as discussed by the authors.
Journal ArticleDOI
Challenges and advances in nanocomposite processing techniques
TL;DR: In this article, the results from numerous studies on various methods for manufacturing nanocomposites with improved properties and retained nanostructures are discussed in detail in detail and recent advances are discussed.
Journal ArticleDOI
Superplastic deformation behaviour of friction stir processed 7075Al alloy
TL;DR: In this article, two fine-grained 7075Al alloys with a grain size of 3.8 and 7.5 μm were subjected to friction stir processing (FSP) with different processing parameters.
Journal ArticleDOI
Dislocation creep behavior in Mg–Al–Zn alloys
TL;DR: In this paper, the authors investigated the climb-controlled dislocation creep behavior of Mg-Al-Zn alloys with different aluminum contents and found that the flow stress increased with the increase of aluminum content under the same deformation conditions.
References
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Book
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John Price Hirth,Jens Lothe +1 more
TL;DR: Dislocations in Isotropic Continua: Effects of Crystal Structure on Dislocations and Dislocation-Point-Defect Interactions at Finite temperatures.
Journal Article
Quantitative microscopy
TL;DR: In this paper, the authors proposed a sampling density for a charge-coupled device (CCD) camera that can be used to evaluate the quality of one's quantitative microscope systems and to identify which components are the "weakest link".
Journal ArticleDOI
Superplasticity—Recent advances and future directions
Oleg D. Sherby,Jeffrey Wadsworth +1 more