Inclination-governed deformation of dislocation-type grain boundaries

Grain boundaries (GBs) in polycrystalline materials are frequently curved, which differ from the well-documented planar GBs in terms of structure and dynamics. However, the physical origin of curvature-controlled GB deformation remains unclear. Here, combining in situ transmission electron microscopy (TEM) nanomechanical testing and atomistic simulation, we rationalize the fundamental influences of GB inclination on the deformation of curved dislocation-type GBs in face-centered cubic metals. Non-uniform motion of curved GB is revealed and attributed to the inclination-dependent dislocation configurations, which simultaneously change the energy and mobility of GBs. An inclination-governed GB model extending from the classic dislocation theory is further established via geometric analyses, where a universal inclination threshold of 35° is deduced to precisely predict the deformation behaviors of curved GBs. These findings enhance our mechanistic understanding of GB-mediated plasticity, shedding light on the structural design of metallic materials via precise GB engineering.