Jiang Lin, Gong Mingyu, Wang Jian, Pan Zhiliang, Wang Xin, Zhang Dalong, Wang Y Morris, Ciston Jim, Minor Andrew M, Xu Mingjie, Pan Xiaoqing, Rupert Timothy J, Mahajan Subhash, Lavernia Enrique J, Beyerlein Irene J, Schoenung Julie M
Department of Materials Science and Engineering, University of California, Irvine, CA, 92697, USA.
Materials & Structural Analysis Division, Thermo Fisher Scientific, Hillsboro, OR, 97124, USA.
Nat Commun. 2022 Jan 10;13(1):20. doi: 10.1038/s41467-021-27591-z.
The abrupt occurrence of twinning when Mg is deformed leads to a highly anisotropic response, making it too unreliable for structural use and too unpredictable for observation. Here, we describe an in-situ transmission electron microscopy experiment on Mg crystals with strategically designed geometries for visualization of a long-proposed but unverified twinning mechanism. Combining with atomistic simulations and topological analysis, we conclude that twin nucleation occurs through a pure-shuffle mechanism that requires prismatic-basal transformations. Also, we verified a crystal geometry dependent twin growth mechanism, that is the early-stage growth associated with instability of plasticity flow, which can be dominated either by slower movement of prismatic-basal boundary steps, or by faster glide-shuffle along the twinning plane. The fundamental understanding of twinning provides a pathway to understand deformation from a scientific standpoint and the microstructure design principles to engineer metals with enhanced behavior from a technological standpoint.
镁发生变形时孪晶的突然出现会导致高度各向异性的响应，使其在结构应用中过于不可靠，在观察中过于不可预测。在此，我们描述了一项针对具有精心设计几何形状的镁晶体的原位透射电子显微镜实验，以可视化一种长期提出但未经验证的孪晶机制。结合原子模拟和拓扑分析，我们得出结论，孪晶成核通过一种需要棱柱面-基面转变的纯重排机制发生。此外，我们验证了一种依赖于晶体几何形状的孪晶生长机制，即与塑性流动不稳定性相关的早期生长，它可以由棱柱面-基面边界台阶的较慢移动主导，也可以由沿孪晶面的较快滑移-重排主导。对孪晶的基本理解从科学角度提供了一条理解变形的途径，从技术角度提供了设计具有增强性能金属的微观结构设计原则。
