Author
A. Mishra
Bio: A. Mishra is an academic researcher from University of California, San Diego. The author has contributed to research in topics: Grain boundary & Deformation (engineering). The author has an hindex of 9, co-authored 12 publications receiving 4232 citations.
Papers
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TL;DR: The mechanical properties of nanocrystalline materials are reviewed in this paper, with emphasis on their constitutive response and on the fundamental physical mechanisms, including the deviation from the Hall-Petch slope and possible negative slope, the effect of porosity, the difference between tensile and compressive strength, the limited ductility, the tendency for shear localization, fatigue and creep responses.
3,828 citations
TL;DR: In this article, the evolution of microstructure and the mechanical response of copper subjected to severe plastic deformation using equal channel angular pressing (ECAP) was investigated, and it was shown that the microstructures produced through adiabatic shear localization during high strain rate deformation and ECAP are very similar.
401 citations
TL;DR: In this article, a modified Johnson-Cook constitutive equation was found to closely capture the dynamic response of ultra-fine-grained (UFG) copper with respect to its deformation.
158 citations
25 Nov 2005-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the mechanisms of microstructural evolution in copper subjected to equal channel angular pressing (ECAP) have been investigated after successive passes, where the first few passes are the most efficient in grain refinement while the microstructure becomes gradually more equiaxed as the number of passes increases.
Abstract: The mechanisms of microstructural evolution in copper subjected to equal channel angular pressing (ECAP) have been investigated after successive passes. The first few passes are the most efficient in grain refinement while the microstructure becomes gradually more equiaxed as the number of passes increases. The texture evolution is discussed based on electron back scattered diffraction (EBSD) results. These experimental results are interpreted in terms of a preliminary model with four successive stages: homogeneous dislocation distribution; elongated sub-cell formation; elongated subgrain formation; break-up of subgrains into equiaxed units; sharpening of grain boundaries and final equiaxed ultrafine structure.
105 citations
TL;DR: A review of the principal mechanisms responsible for the plastic deformation of nanocrystalline metals can be found in this article, where the authors show that with a decrease in grain size there is a gradual shift in the relative importance of the deformation mechanisms away from the ones operating in the conventional polycrystalline domain.
Abstract: This article presents a review of the principal mechanisms responsible for the plastic deformation of nanocrystalline metals. As the concentration of grain boundaries increases, with a decrease in grain size there is a gradual shift in the relative importance of the deformation mechanisms away from the ones operating in the conventional polycrystalline domain. This is predicted by molecular dynamics simulations that indicate a preponderance of dislocation emission/annihilation at grain boundaries and grain-boundary sliding when grain sizes are in the range 20–50 nm. Experiments show, in general, a saturation in work hardening at low strains, which is indicative of a steady-state dislocation density. This saturation is accompanied by an increased tendency toward shear localization, which is supportive of dislocation generation and annihilation at grain boundaries. Dislocation analyses recently proposed corroborate the computational predictions and provide a rational foundation for understanding the mechanical response.
76 citations
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TL;DR: The methods of making nanoparticles using plant extracts are reviewed, methods of particle characterization are reviewed and potential applications of the particles in medicine are discussed.
1,706 citations
TL;DR: The maximum strength of nanotwinned copper samples with different twin thicknesses is investigated, finding that the strength increases with decreasing twin thickness, reaching a maximum at 15 nanometers, followed by a softening at smaller values that is accompanied by enhanced strain hardening and tensile ductility.
Abstract: [Lu, L.; Chen, X.; Lu, K.] Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Peoples R China. [Huang, X.] Tech Univ Denmark, Riso Natl Lab Sustainable Energy, Ctr Fundamental Res Met Struct Four Dimens, Dept Mat Res, DK-4000 Roskilde, Denmark.;Lu, L (reprint author), Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Peoples R China;llu@imr.ac.cn
1,602 citations
TL;DR: In this paper, the authors provide an overview of metal-based material classes whose properties as a function of external size have been investigated and provide a critical discussion on the combined effects of intrinsic and extrinsic sizes on the material deformation behavior.
1,515 citations
TL;DR: A brief overview of the available SPD technologies is given in this paper, along with a summary of unusual mechanical, physical and other properties achievable by SPD processing, as well as the challenges this research is facing, some of them generic and some specific to the nanoSPD area.
1,451 citations
TL;DR: The extraordinary intrinsic plasticity of gradient NG structures offers their potential for use as advanced coatings of bulk materials in both high strength and ductility materials.
Abstract: Nano-grained (NG) metals are believed to be strong but intrinsically brittle: Free-standing NG metals usually exhibit a tensile uniform elongation of a few percent. When a NG copper film is confined by a coarse-grained (CG) copper substrate with a gradient grain-size transition, tensile plasticity can be achieved in the NG film where strain localization is suppressed. The gradient NG film exhibits a 10 times higher yield strength and a tensile plasticity comparable to that of the CG substrate and can sustain a tensile true strain exceeding 100% without cracking. A mechanically driven grain boundary migration process with a substantial concomitant grain growth dominates plastic deformation of the gradient NG structure. The extraordinary intrinsic plasticity of gradient NG structures offers their potential for use as advanced coatings of bulk materials.
1,198 citations