Tian Yuan, Gong Xiaoguo, Xu Mingjie, Qiu Caihao, Han Ying, Bi Yutong, Estrada Leonardo Velasco, Boltynjuk Evgeniy, Hahn Horst, Han Jian, Srolovitz David J, Pan Xiaoqing
Department of Materials Science and Engineering, University of California, Irvine, CA, USA.
Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China.
Science. 2024 Oct 4;386(6717):49-54. doi: 10.1126/science.adk6384. Epub 2024 Oct 3.
Near-rigid-body grain rotation is commonly observed during grain growth, recrystallization, and plastic deformation in nanocrystalline materials. Despite decades of research, the dominant mechanisms underlying grain rotation remain enigmatic. We present direct evidence that grain rotation occurs through the motion of disconnections (line defects with step and dislocation character) along grain boundaries in platinum thin films. State-of-the-art in situ four-dimensional scanning transmission electron microscopy (4D-STEM) observations reveal the statistical correlation between grain rotation and grain growth or shrinkage. This correlation arises from shear-coupled grain boundary migration, which occurs through the motion of disconnections, as demonstrated by in situ high-angle annular dark-field STEM observations and the atomistic simulation-aided analysis. These findings provide quantitative insights into the structural dynamics of nanocrystalline materials.
在纳米晶材料的晶粒生长、再结晶和塑性变形过程中，通常会观察到近刚体晶粒旋转。尽管经过了数十年的研究，但晶粒旋转背后的主导机制仍然不明。我们提供了直接证据，表明晶粒旋转是通过铂薄膜中沿晶界的位错间断（具有台阶和位错特征的线缺陷）运动而发生的。先进的原位四维扫描透射电子显微镜（4D-STEM）观察揭示了晶粒旋转与晶粒生长或收缩之间的统计相关性。这种相关性源于剪切耦合晶界迁移，它是通过位错间断的运动发生的，原位高角度环形暗场STEM观察和原子模拟辅助分析证明了这一点。这些发现为纳米晶材料的结构动力学提供了定量见解。
