In Situ Atomic‐Scale Experiments Reveal the Atomistic Mechanisms of Grain Boundary Plasticity

Abstract Grain boundary (GB) plastic deformation is a critical deformation mode that can significantly affect the microstructure and mechanical properties of metals. Given its importance, numerous studies have been conducted over the past few decades to investigate the atomistic mechanism of GB plasticity, which includes GB migration, GB sliding, and grain rotation. These three deformation modes typically occur simultaneously and interact cooperatively. Despite substantial advancements in understanding the atomic‐scale mechanisms of GB plasticity, there is a scarcity of review papers addressing the in situ atomic‐scale mechanisms of GB plasticity. This work aims to provide a comprehensive overview of the atomistic mechanisms of GB plasticity in metals, detailing modes predicted by theoretical models and molecular dynamics (MD) simulations, as well as discussing mechanisms verified by in situ atomic‐scale experiments. Additionally, it examines the factors influencing GB deformation. The authors intend for this review to serve not only as a valuable resource for researchers in the field of nanocrystalline (NC) metals but also as a textbook for educating graduate students.