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A classical equation that accounts for observations of non-Arrhenius and cryogenic grain boundary migration
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作者 Eric R.Homer Oliver K.Johnson +3 位作者 Darcey Britton James E.Patterson Eric T.Sevy gregory b.thompson 《npj Computational Materials》 SCIE EI CSCD 2022年第1期1492-1500,共9页
Observations of microstructural coarsening at cryogenic temperatures,as well as numerous simulations of grain boundary motion that show faster migration at low temperature than at high temperature,have been troubling ... Observations of microstructural coarsening at cryogenic temperatures,as well as numerous simulations of grain boundary motion that show faster migration at low temperature than at high temperature,have been troubling because they do not follow the expected Arrhenius behavior.This work demonstrates that classical equations,that are not simplified,account for all these oddities and demonstrate that non-Arrhenius behavior can emerge from thermally activated processes.According to this classical model,this occurs when the intrinsic barrier energies of the processes become small,allowing activation at cryogenic temperatures.Additional thermal energy then allows the low energy process to proceed in reverse,so increasing temperature only serves to frustrate the forward motion.This classical form is shown to reconcile and describe a variety of diverse grain boundary migration observations. 展开更多
关键词 CRYOGENIC GRAIN BOUNDARY
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On the mechanistic origins of maximum strength in nanocrystalline metals
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作者 Ankit Gupta Jacob Gruber +3 位作者 Satish S.Rajaram gregory b.thompson David L.McDowell Garritt J.Tucker 《npj Computational Materials》 SCIE EI CSCD 2020年第1期393-404,共12页
The maximum strength of polycrystalline metals/alloys has been suggested to occur at nanoscale grain sizes where the governing deformation mechanism transitions from dislocation plasticity to grain boundary mediated d... The maximum strength of polycrystalline metals/alloys has been suggested to occur at nanoscale grain sizes where the governing deformation mechanism transitions from dislocation plasticity to grain boundary mediated deformation.Despite tremendous progress recently uncovering links between transitions in nanoscale mechanisms and peak strength,the scientific literature is mostly devoid of any quantitative support,owing to the difficulty in measuring the resolved contribution of individual mechanisms to microstructural strain accommodation.In this study,the contribution of individual nanoscale mechanisms to the overall deformation of nanocrystalline Ni is calculated from atomistic simulations leveraging continuum-based kinematic metrics to compute mechanistic contributions to microstructural strain. 展开更多
关键词 STRENGTH DEFORMATION GRAIN
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