Grain boundary mediated plasticity (e.g., grain rotation and grain boundary sliding) plays a critical role in determining the deformation behavior of polycrystals, which is especially important for nanocrystalline metals or plastic deformation at elevated temperatures. However, due to the lack of a theoretical framework, the mechanism of deformation-induced grain rotation has not been well understood. By introducing a disclination-based description, we show that crystal rotation can be captured conveniently through the characteristic rotational vector of a disclination (i.e., the Frank vector). Under the framework of topological defect theory, grain boundary mediated plasticity can be treated as topological reactions between dislocations and disclinations, leading to rigorous predictions of grain/subgrain rotation through a pseudo-inverse solution for the reformulated Frank-Bilby equation. Systematic classifications of grain/subgrain rotation and grain boundary formation are raised for hexagonal close-packed (HCP) metals, which has been validated by Electron-Backscattered Diffraction characterizations in Mg alloys. Our work not only suggests a theoretical approach to investigate grain/subgrain rotation based on the topological correlation between dislocations and disclinations, but also provides a new insight into the plastic behaviors of polycrystalline HCP metals.

晶界介导的塑性（例如，晶粒旋转和晶界滑动）在决定多晶的变形行为中起着关键作用，这对于纳米晶金属或高温下的塑性变形尤其重要。然而，由于缺乏理论框架，变形诱导晶粒旋转的机制尚未得到很好的理解。通过引入基于向错的描述，我们表明可以通过向错的特征旋转矢量（即 Frank 矢量）方便地捕获晶体旋转。在拓扑缺陷理论的框架下，晶界介导的塑性可以被视为位错和向错之间的拓扑反应，通过重新制定的 Frank-Bilby 方程的伪逆解，导致对晶粒/亚晶粒旋转的严格预测。六方密排 (HCP) 金属提出了晶粒/亚晶粒旋转和晶界形成的系统分类，这已通过镁合金中的电子背散射衍射表征得到验证。我们的工作不仅提出了一种基于位错和向错之间的拓扑相关性来研究晶粒/亚晶粒旋转的理论方法，而且还为多晶 HCP 金属的塑性行为提供了新的见解。这已通过镁合金中的电子背散射衍射表征得到验证。我们的工作不仅提出了一种基于位错和向错之间的拓扑相关性来研究晶粒/亚晶粒旋转的理论方法，而且还为多晶 HCP 金属的塑性行为提供了新的见解。这已通过镁合金中的电子背散射衍射表征得到验证。我们的工作不仅提出了一种基于位错和向错之间的拓扑相关性来研究晶粒/亚晶粒旋转的理论方法，而且还为多晶 HCP 金属的塑性行为提供了新的见解。