Athermal mechanisms of size-dependent crystal flow gleaned from three-dimensional discrete dislocation simulations
Athermal mechanisms of size-dependent crystal flow gleaned from three-dimensional discrete dislocation simulations
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DOI：
10.1016/j.actamat.2008.03.011
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发表时间：
2008-08
期刊：
影响因子：
9.4
通讯作者：
S. Rao;D. Dimiduk;T. Parthasarathy;M. Uchic;M. Tang;C. Woodward
中科院分区：
文献类型：
--
作者：
S. Rao;D. Dimiduk;T. Parthasarathy;M. Uchic;M. Tang;C. Woodward
最近的实验研究表明，微米尺度的面心立方（fcc）晶体显示出强烈的强化效应，即使在高初始位错密度。我们使用大规模三维离散位错模拟（DDS）来明确地模拟尺寸范围为0.5-20μm的fcc Ni微晶的变形行为。这项研究表明，两个尺寸敏感的非热硬化过程，超越森林硬化，是足以开发的尺寸缩放的流动应力，随机应力变化，流动不稳定性和高初始应变硬化率，类似于各种材料的实验观察。一种机制，源截断硬化，在微米级体积中特别有效。第二种机制，称为耗尽硬化，从森林硬化的平均场条件的小体积的故障，从而偏置普通位错过程的统计结果。
Recent experimental studies have revealed that micrometer-scale face-centered cubic (fcc) crystals show strong strengthening effects, even at high initial dislocation densities. We use large-scale three-dimensional discrete dislocation simulations (DDS) to explicitly model the deformation behavior of fcc Ni microcrystals in the size range of 0.5–20μm. This study shows that two size-sensitive athermal hardening processes, beyond forest hardening, are sufficient to develop the dimensional scaling of the flow stress, stochastic stress variation, flow intermittency and high initial strain-hardening rates, similar to experimental observations for various materials. One mechanism, source-truncation hardening, is especially potent in micrometer-scale volumes. A second mechanism, termed exhaustion hardening, results from a breakdown of the mean-field conditions for forest hardening in small volumes, thus biasing the statistics of ordinary dislocation processes.