发表机构
RWTH Aachen University; CNRS, Université de Lorraine, Arts et Métiers Institute of Technology; Helmholtz Zentrum Hereon（亚琛工业大学; 法国国家科学研究中心，洛林大学，国立工艺学院; 海姆霍兹HEREON中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究结合原位微力学测试与原子模拟，揭示镁受限体积内随机孪生的起源源于局部缺陷结构导致的竞争孪生路径的随机选择，为相关材料提供了通用框架。
AI 中文摘要
拉伸孪生在镁的c轴塑性协调中发挥核心作用。在块状镁中，孪生通常表现出相对确定的响应，临界应力较低；而在受限体积内，孪生表现出明显的分散性，使小尺度力学行为的预测变得复杂。本研究结合位点特异性微柱压缩与原子模拟，探究这种随机性的起源。实验表明，在a轴压缩下，塑性变形由{10-12}孪生主导，应力-应变响应中的每个离散应力降都标志着一个孪晶的激活与快速扩展。原子模拟进一步将孪生分为两种机制 regime：形核与纵向扩展发生在高应力、 shuffle辅助的 regime中，而横向增厚则在由位错滑移控制的低应力 regime中进行。将这些机制见解与变形微柱的事后表征相结合，表明测得屈服应力的分散性源于竞争孪生路径间的随机选择，这种选择由局部缺陷结构（预存缺陷的存在、分布与形态）决定。总体而言，本研究确定了镁中尺寸依赖的随机孪生的原子基础，并为塑性受离散激活事件控制的材料提供了通用框架。
英文摘要
Tensile twinning plays a central role in accommodating <c>-axis plasticity in Mg. In bulk Mg, it typically shows a relatively deterministic response with a low critical stress, whereas in confined volumes it exhibits broad yield-stress distributions that complicate the prediction of small-scale mechanical behavior. Here, site-specific compression tests are performed on 4 $μ$m-diameter pillars fabricated in a parent Mg crystal and an adjacent {10-12} twin. The two regions share the same [11-20] compression axis but experienced different prior deformation histories, allowing the influence of the residual microstructural state to be examined at fixed crystallographic orientation. Among 27 pillars, most parent-region pillars yield near 300 MPa, whereas pillars from the twin region span approximately 30 to 300 MPa. Interrupted tests combined with cross-sectional EBSD link individual load drops to discrete twin formation and further show that a pillar containing a pre-existing twin yields at approximately 80 MPa through the migration of the existing twin boundary. Molecular dynamics simulations of 30 nm-diameter pillars resolve possible atomistic pathways at the nanoscale. The simulations illustrate how contact geometry and pre-existing twin embryos alter event selection, and how an activated twin advances rapidly, while coherent twin boundary migration proceeds through disconnection motion accompanied by crystallographically required atomic shuffles. The results attribute the experimental scatter to the local availability of embryos and mobile interfaces, such that the first plastic event is governed by the twinning pathway accessible from the local microstructural state rather than by a single characteristic critical stress. Deformation history can therefore strongly modify the distribution of first plastic events even when the loading orientation is fixed.
