Qiu Caihao, Srolovitz David J, Rohrer Gregory S, Han Jian, Salvalaglio Marco
Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong Special Administrative Regions of China.
Department of Mechanical Engineering, The University of Hong Kong, Hong Kong Special Administrative Regions of China.
Proc Natl Acad Sci U S A. 2025 Jun 17;122(24):e2500707122. doi: 10.1073/pnas.2500707122. Epub 2025 Jun 12.
Grain growth in polycrystals is traditionally considered a capillarity-driven process, where grain boundaries (GBs) migrate toward their centers of curvature (i.e., mean curvature flow) with a velocity proportional to the local curvature (including extensions to account for anisotropic GB energy and mobility). Experimental and simulation evidence shows that this simplistic view is untrue. We demonstrate that the failure of the classical mean curvature flow description of grain growth mainly originates from the shear deformation naturally coupled with GB motion (i.e., shear coupling). Our findings are built on large-scale microstructure evolution simulations incorporating the fundamental (crystallography-respecting) microscopic mechanism of GB migration. The nature of the deviations from curvature flow revealed in our simulations is consistent with observations in recent experimental studies on different materials. This work also demonstrates how to incorporate the mechanical effects that are essential to the accurate prediction of microstructure evolution.
多晶体中的晶粒生长传统上被认为是一个由毛细作用驱动的过程，其中晶界（GBs）朝着其曲率中心迁移（即平均曲率流），迁移速度与局部曲率成正比（包括考虑各向异性晶界能量和迁移率的扩展情况）。实验和模拟证据表明，这种简单的观点并不正确。我们证明，经典的平均曲率流对晶粒生长的描述失效主要源于与晶界运动自然耦合的剪切变形（即剪切耦合）。我们的发现基于大规模微观结构演化模拟，该模拟纳入了晶界迁移的基本（尊重晶体学）微观机制。我们模拟中揭示的与曲率流偏差的性质与近期对不同材料的实验研究中的观察结果一致。这项工作还展示了如何纳入对微观结构演化准确预测至关重要的力学效应。
