Competition between shear localization and tensile detwinning in twinned nanowires
Competition between shear localization and tensile detwinning in twinned nanowires
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DOI：
10.1103/physrevmaterials.4.023603
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发表时间：
2020-02
影响因子：
3.4
通讯作者：
Sheng Yin;G. Cheng;Yong Zhu;Huajian Gao
中科院分区：
文献类型：
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作者：
Sheng Yin;G. Cheng;Yong Zhu;Huajian Gao
最近，在具有平行于纳米线长度的孪晶边界的双缠绕金属纳米线中，发现了从局域位错滑移到离域塑性的变形机制的转变，这种转变是通过反常的拉伸去孪晶机制实现的.然而，实验表明，在大多数bitwinned纳米线的异常拉伸解孪晶不传播通过整个NW，这限制了纳米线的破坏应变相比，在单晶纳米线的孪晶诱导的超塑性。一个难以捉摸的，但根本上重要的问题是，什么因素可能会影响这种bitwinned纳米线的拉伸解孪晶的传播。此外，这种拉伸去孪晶机制是否可以应用于其他类型的孪晶纳米线？在这里，原位透射电子显微镜测试和分子动力学模拟的基础上，剪切定位和拉伸解孪晶之间的竞争被确定。通过将拉伸去孪晶机制分为两个步骤并分别研究每个步骤，发现在步骤1期间形成的单晶胚的质量决定随后的去孪晶传播（步骤2）和最终的塑性应变。此外，这种反常的拉伸退孪机制被扩展到具有平行于长度方向的多个TB的其他金属纳米线，例如不对称的五缠绕纳米线和具有多个平行TB的纳米线。这项工作突出了在大塑性金属纳米线与不同的孪晶结构的脱孪晶的重要作用。
Recently, a transition of deformation mechanism from localized dislocation slip to delocalized plasticity via an anomalous tensile detwinning mechanism has been discovered in bitwinned metallic nanowires (NWs) with a single twin boundary (TB) running parallel to the NW length. However, experiments showed that the anomalous tensile detwinning in most of bitwinned NWs does not propagate through the whole NW, which limits the NWs failure strain when compared to the twinning-induced superplasticity in single-crystalline NWs. An elusive but fundamentally important question is that what factors might affect the propagation of tensile detwinning in such bitwinned NWs. In addition, can this tensile detwinning mechanism be applied to other types of twinned NWs? Here, based on in situ transmission electron microscopy testing and molecular dynamics simulations, a competition between shear localization and tensile detwinning is identified. By dividing the tensile detwinning mechanism into two steps and investigating each step separately, it is found that the quality of a single-crystalline embryo formed during step one determines the succeeding detwinning propagation (step two) and the final plastic strain. Furthermore, this anomalous tensile detwinning mechanism is extended to other metallic NWs with multiple TBs running parallel to the length direction, such as asymmetric pentatwinned NWs and NWs with multiple parallel TBs. This work highlights the important role of detwinning in large plasticity in metallic NWs with different twin structures.