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.

中文翻译：

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纳米晶材料中的晶粒旋转机制：Pt 薄膜中的多尺度观测


在纳米晶材料的晶粒生长、再结晶和塑性变形过程中，通常观察到近刚体晶粒旋转。尽管进行了数十年的研究，但粮食轮作的主要机制仍然是个谜。我们提供了直接证据，证明晶粒旋转是通过铂薄膜中沿晶界的断开运动（具有阶梯和位错特性的线缺陷）发生的。最先进的原位四维扫描透射电子显微镜 （4D-STEM） 观察揭示了晶粒轮动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，这是通过断开运动发生的，原位高角度环形暗场 STEM 观测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。