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S Suresh - One of the best experts on this subject based on the ideXlab platform.
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interfacial plasticity governs strain Rate Sensitivity and ductility in nanostructured metals
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Ju Li, Amit Samanta, S SureshAbstract:Nano-twinned copper exhibits an unusual combination of ultrahigh strength and high ductility, along with increased strain-Rate Sensitivity. We develop a mechanistic framework for predicting the Rate Sensitivity and elucidating the origin of ductility in terms of the interactions of dislocations with interfaces. Using atomistic reaction pathway calculations, we show that slip transfer reactions mediated by twin boundary are the Rate-controlling mechanisms of plastic flow. We attribute the relatively high ductility of nano-twinned copper to the hardening of twin boundaries as they gradually lose coherency during plastic deformation. These findings provide insights into the possible means of optimizing strength and ductility through interfacial engineering.
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strength strain Rate Sensitivity and ductility of copper with nanoscale twins
Acta Materialia, 2006Co-Authors: L Lu, Yongfeng Shen, S SureshAbstract:We present a comprehensive computational analysis of the deformation of ultrafine crystalline pure Cu with nanoscale growth twins. This physically motivated model benefits from our experimental studies of the effects of the density of coherent nanotwins on the plastic deformation characteristics of Cu, and from post-deformation transmission electron microscopy investigations of dislocation structures in the twinned metal. The analysis accounts for high plastic anisotropy and Rate Sensitivity anisotropy by treating the twin boundary as an internal interface and allowing special slip geometry arrangements that involve soft and hard modes of deformation. This model correctly predicts the experimentally observed trends of the effects of twin density on flow strength, Rate Sensitivity of plastic flow and ductility, in addition to matching many of the quantitative details of plastic deformation reasonably well. The computational simulations also provide critical mechanistic insights into why the metal with nanoscale twins can provide the same level of yield strength, hardness and strain Rate Sensitivity as a nanostructured counterpart without twins (but of grain size comparable to the twin spacing of the twinned Cu). The analysis also offers some useful understanding of why the nanotwinned Cu with high strength does not lead to diminished ductility with structural refinement involving twins, whereas nanostructured Cu normally causes the ductility to be compromised at the expense of strength upon grain refinement.
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strain Rate Sensitivity of cu with nanoscale twins
Scripta Materialia, 2006Co-Authors: Yongfeng Shen, L Lu, S SureshAbstract:The strain-Rate Sensitivity of ultrafine-crystalline Cu with different concentrations of nanoscale growth twins is investigated using tensile strain Rate jump tests. Higher twin density leads to enhanced Rate Sensitivity, which decreases mildly with increasing strain Rate and strain. Mechanisms underlying these effects are explored through post-deformation transmission electron microscopy.
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some critical experiments on the strain Rate Sensitivity of nanocrystalline nickel
Acta Materialia, 2003Co-Authors: Ruth Schwaiger, B Moser, N Chollacoop, S SureshAbstract:Systematic experiments have been performed to investigate the Rate Sensitivity of deformation in fully dense nanocrystalline Ni using two different experimental techniques: depth-sensing indentation and tensile testing. Results from both types of tests reveal that the strain-Rate Sensitivity is a strong function of grain size. Specifically microcrystalline and ultra-fine crystalline pure Ni, with grain size range of 1 µm and 100–1000 nm, respectively, exhibit essentially Rateindependent plastic flow over the range 3 × 10 4 to 3 × 10 1 s 1 , whereas nanocrystalline pure Ni with a grain size of approximately 40 nm, exhibits marked Rate Sensitivity over the same range. A simple computational model, predicated on the premise that a Rate-sensitive grain-boundary affected zone exists, is shown to explain the observed effect of grain size on the Rate-dependent plastic response. 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Frederic Barlat - One of the best experts on this subject based on the ideXlab platform.
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strain hardening Rate Sensitivity and strain Rate Sensitivity in twip steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Alexandra Bintu, Gabriela Vincze, José Joaquin De Almeida Gracio, Catalin R Picu, A B Lopes, Frederic BarlatAbstract:Abstract TWIP steels are materials with very high strength and exceptional strain hardening capability, parameters leading to large energy absorption before failure. However, TWIP steels also exhibit reduced (often negative) strain Rate Sensitivity (SRS) which limits the post-necking deformation. In this study we demonstRate for an austenitic TWIP steel with 18% Mn a strong dependence of the twinning Rate on the strain Rate, which results in negative strain hardening Rate Sensitivity (SHRS). The instantaneous component of SHRS is large and negative, while its transient is close to zero. The SRS is observed to decrease with strain, becoming negative for larger strains. Direct observations of the strain Rate dependence of the twinning Rate are made using electron microscopy and electron backscatter diffraction, which substantiate the proposed mechanism for the observed negative SHRS.
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Effect of solute distribution on the strain Rate Sensitivity of solid solutions
Scripta Materialia, 2006Co-Authors: R C Picu, Gabriela Vincze, José Joaquin De Almeida Gracio, Frederic BarlatAbstract:Abstract An experimental study is presented regarding the effect of pre-existing inhomogeneous solute distribution on the strain Rate Sensitivity of a non-heat treatable Al–Mg alloy (AA5182). Tests are performed with specimens heat treated to eliminate pre-existing solute structures within the material and with specimens equilibRated at room temperature. The Rate Sensitivity is significantly more pronounced in the equilibRated specimens, which indicates that solute structures that exist before the test play a role in determining the Rate Sensitivity of the material at low temperatures.
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strain Rate Sensitivity of the commercial aluminum alloy aa5182 o
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: R C Picu, Gabriela Vincze, José Joaquin De Almeida Gracio, Fahrettin Ozturk, Frederic Barlat, Antoinette M ManiattyAbstract:The mechanical behavior of the commercial aluminum alloy AA5182-O is investigated at temperatures ranging from −120 to 150 ◦ C and strain Rates from 10 −6 to 10 −1 s −1 . The strain Rate Sensitivity parameter is determined as a function of temperature and plastic strain, and the strain Rate and temperature range in which dynamic strain aging leads to negative strain Rate Sensitivity is mapped. The effect of dynamic strain aging on ductility and strain hardening is investigated. The Sensitivity of the measured quantities to the experimental method employed and their dependence on grain shape are discussed. The experimental data are compared with the predictions of a model constructed based on a recently proposed mechanism for dynamic strain ageing. The mechanism is based on the effect solute clustering at forest dislocations has on the strength of dislocation junctions. The model is shown to reproduce qualitatively the experimental trends. © 2004 Elsevier B.V. All rights reserved.
L Lu - One of the best experts on this subject based on the ideXlab platform.
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strength strain Rate Sensitivity and ductility of copper with nanoscale twins
Acta Materialia, 2006Co-Authors: L Lu, Yongfeng Shen, S SureshAbstract:We present a comprehensive computational analysis of the deformation of ultrafine crystalline pure Cu with nanoscale growth twins. This physically motivated model benefits from our experimental studies of the effects of the density of coherent nanotwins on the plastic deformation characteristics of Cu, and from post-deformation transmission electron microscopy investigations of dislocation structures in the twinned metal. The analysis accounts for high plastic anisotropy and Rate Sensitivity anisotropy by treating the twin boundary as an internal interface and allowing special slip geometry arrangements that involve soft and hard modes of deformation. This model correctly predicts the experimentally observed trends of the effects of twin density on flow strength, Rate Sensitivity of plastic flow and ductility, in addition to matching many of the quantitative details of plastic deformation reasonably well. The computational simulations also provide critical mechanistic insights into why the metal with nanoscale twins can provide the same level of yield strength, hardness and strain Rate Sensitivity as a nanostructured counterpart without twins (but of grain size comparable to the twin spacing of the twinned Cu). The analysis also offers some useful understanding of why the nanotwinned Cu with high strength does not lead to diminished ductility with structural refinement involving twins, whereas nanostructured Cu normally causes the ductility to be compromised at the expense of strength upon grain refinement.
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strain Rate Sensitivity of cu with nanoscale twins
Scripta Materialia, 2006Co-Authors: Yongfeng Shen, L Lu, S SureshAbstract:The strain-Rate Sensitivity of ultrafine-crystalline Cu with different concentrations of nanoscale growth twins is investigated using tensile strain Rate jump tests. Higher twin density leads to enhanced Rate Sensitivity, which decreases mildly with increasing strain Rate and strain. Mechanisms underlying these effects are explored through post-deformation transmission electron microscopy.
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hardness and strain Rate Sensitivity of nanocrystalline cu
Scripta Materialia, 2006Co-Authors: Jing Chen, L Lu, K LuAbstract:The measured hardness of nanocrystalline Cu with grain sizes (( as small as 10 nm still follows the Hall-Petch relation. A Rate Sensitivity of 0.06 +/- 0.01 and a flow stress activation volume of 8b(3) were determined at d = 10 nm, suggesting grain boundary activities are enhanced but not yet dominant in the plastic deformation. (c) 2006 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.
Gabriela Vincze - One of the best experts on this subject based on the ideXlab platform.
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strain hardening Rate Sensitivity and strain Rate Sensitivity in twip steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Alexandra Bintu, Gabriela Vincze, José Joaquin De Almeida Gracio, Catalin R Picu, A B Lopes, Frederic BarlatAbstract:Abstract TWIP steels are materials with very high strength and exceptional strain hardening capability, parameters leading to large energy absorption before failure. However, TWIP steels also exhibit reduced (often negative) strain Rate Sensitivity (SRS) which limits the post-necking deformation. In this study we demonstRate for an austenitic TWIP steel with 18% Mn a strong dependence of the twinning Rate on the strain Rate, which results in negative strain hardening Rate Sensitivity (SHRS). The instantaneous component of SHRS is large and negative, while its transient is close to zero. The SRS is observed to decrease with strain, becoming negative for larger strains. Direct observations of the strain Rate dependence of the twinning Rate are made using electron microscopy and electron backscatter diffraction, which substantiate the proposed mechanism for the observed negative SHRS.
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Effect of solute distribution on the strain Rate Sensitivity of solid solutions
Scripta Materialia, 2006Co-Authors: R C Picu, Gabriela Vincze, José Joaquin De Almeida Gracio, Frederic BarlatAbstract:Abstract An experimental study is presented regarding the effect of pre-existing inhomogeneous solute distribution on the strain Rate Sensitivity of a non-heat treatable Al–Mg alloy (AA5182). Tests are performed with specimens heat treated to eliminate pre-existing solute structures within the material and with specimens equilibRated at room temperature. The Rate Sensitivity is significantly more pronounced in the equilibRated specimens, which indicates that solute structures that exist before the test play a role in determining the Rate Sensitivity of the material at low temperatures.
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strain Rate Sensitivity of the commercial aluminum alloy aa5182 o
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: R C Picu, Gabriela Vincze, José Joaquin De Almeida Gracio, Fahrettin Ozturk, Frederic Barlat, Antoinette M ManiattyAbstract:The mechanical behavior of the commercial aluminum alloy AA5182-O is investigated at temperatures ranging from −120 to 150 ◦ C and strain Rates from 10 −6 to 10 −1 s −1 . The strain Rate Sensitivity parameter is determined as a function of temperature and plastic strain, and the strain Rate and temperature range in which dynamic strain aging leads to negative strain Rate Sensitivity is mapped. The effect of dynamic strain aging on ductility and strain hardening is investigated. The Sensitivity of the measured quantities to the experimental method employed and their dependence on grain shape are discussed. The experimental data are compared with the predictions of a model constructed based on a recently proposed mechanism for dynamic strain ageing. The mechanism is based on the effect solute clustering at forest dislocations has on the strength of dislocation junctions. The model is shown to reproduce qualitatively the experimental trends. © 2004 Elsevier B.V. All rights reserved.
José Joaquin De Almeida Gracio - One of the best experts on this subject based on the ideXlab platform.
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strain hardening Rate Sensitivity and strain Rate Sensitivity in twip steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Alexandra Bintu, Gabriela Vincze, José Joaquin De Almeida Gracio, Catalin R Picu, A B Lopes, Frederic BarlatAbstract:Abstract TWIP steels are materials with very high strength and exceptional strain hardening capability, parameters leading to large energy absorption before failure. However, TWIP steels also exhibit reduced (often negative) strain Rate Sensitivity (SRS) which limits the post-necking deformation. In this study we demonstRate for an austenitic TWIP steel with 18% Mn a strong dependence of the twinning Rate on the strain Rate, which results in negative strain hardening Rate Sensitivity (SHRS). The instantaneous component of SHRS is large and negative, while its transient is close to zero. The SRS is observed to decrease with strain, becoming negative for larger strains. Direct observations of the strain Rate dependence of the twinning Rate are made using electron microscopy and electron backscatter diffraction, which substantiate the proposed mechanism for the observed negative SHRS.
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Effect of solute distribution on the strain Rate Sensitivity of solid solutions
Scripta Materialia, 2006Co-Authors: R C Picu, Gabriela Vincze, José Joaquin De Almeida Gracio, Frederic BarlatAbstract:Abstract An experimental study is presented regarding the effect of pre-existing inhomogeneous solute distribution on the strain Rate Sensitivity of a non-heat treatable Al–Mg alloy (AA5182). Tests are performed with specimens heat treated to eliminate pre-existing solute structures within the material and with specimens equilibRated at room temperature. The Rate Sensitivity is significantly more pronounced in the equilibRated specimens, which indicates that solute structures that exist before the test play a role in determining the Rate Sensitivity of the material at low temperatures.
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strain Rate Sensitivity of the commercial aluminum alloy aa5182 o
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: R C Picu, Gabriela Vincze, José Joaquin De Almeida Gracio, Fahrettin Ozturk, Frederic Barlat, Antoinette M ManiattyAbstract:The mechanical behavior of the commercial aluminum alloy AA5182-O is investigated at temperatures ranging from −120 to 150 ◦ C and strain Rates from 10 −6 to 10 −1 s −1 . The strain Rate Sensitivity parameter is determined as a function of temperature and plastic strain, and the strain Rate and temperature range in which dynamic strain aging leads to negative strain Rate Sensitivity is mapped. The effect of dynamic strain aging on ductility and strain hardening is investigated. The Sensitivity of the measured quantities to the experimental method employed and their dependence on grain shape are discussed. The experimental data are compared with the predictions of a model constructed based on a recently proposed mechanism for dynamic strain ageing. The mechanism is based on the effect solute clustering at forest dislocations has on the strength of dislocation junctions. The model is shown to reproduce qualitatively the experimental trends. © 2004 Elsevier B.V. All rights reserved.
