npj: 晶界影响孪晶形成

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一些面心立方金属晶界处常可观察到变形孪晶形成（deformation twinning）。孪晶形成于晶界处，一个可能的促进因素是，晶粒变形时的晶粒间相互作用。但晶粒间力学相互作用对孪晶演化有何影响，人们并不十分清楚。同时，晶界微结构特征与孪晶形成之间的因果关系虽有大量实验和模拟研究，但仍不清楚大量晶粒聚集体之间的关系。来自韩国浦项科技大学的金贤勋及其同事，基于变形钢的位错滑移和孪生机制，对金属微观结构（由各种取向的晶粒合成而来）中的变形行为进行模拟并结合电子背散射衍射技术发现，孪晶首先起始于晶粒边界附近，并依赖初始晶粒的取向。随着进一步的变形，晶界一侧强大的孪晶活性，又在该晶界的另一侧引发了强烈的孪晶活性。甚至不利于孪晶形成的晶粒却由于周围晶粒的相互作用，而促进了孪晶形成。因此，研究相邻晶粒间的邻接关系很可能有助于优化由孪晶形成的合金。该文近期发表于npj Computational Materials 3:21,2017; doi:10.1038/s41524-017-0023-1，英文标题与摘要如下。点击阅读原文可以自由下载论文PDF。

Continuum understanding of twin formation near grain boundaries of FCC metals with low stacking fault energy 

Jaimyun Jung, Jae Ik Yoon, Jung Gi Kim, Marat I. Latypov, Jin You Kim & Hyoung Seop Kim

Deformation twinning from grain boundaries is often observed in face-centered cubic metals with low stacking fault energy. One of the possible factors that contribute to twinning origination from grain boundaries is the intergranular interactions during deformation. Nonetheless, the influence of mechanical interaction among grains on twin evolution has not been fully understood. In spite of extensive experimental and modeling efforts on correlating microstructural features with their twinning behavior, a clear relation among the large aggregate of grains is still lacking. In this work, we characterize the micromechanics of grain-to-grain interactions that contribute to twin evolution by investigating the mechanical twins near grain boundaries using a full-field crystal plasticity simulation of a twinning-induced plasticity steel deformed in uniaxial tension at room temperature. Microstructures are first observed through electron backscatter diffraction technique to obtain data to reconstruct a statistically equivalent microstructure through synthetic microstructure building. Grain-to-grain micromechanical response is analyzed to assess the collective twinning behavior of the microstructural volume element under tensile deformation. Examination of the simulated results reveal that grain interactions are capable of changing the local mechanical behavior near grain boundaries by transferring strain across grain boundary or localizing strain near grain boundary.

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