Disconnection flow-mediated grain rotation

• 成果类型: Article
• 署名作者: Qiu, Caihao; Salvalaglio, Marco; Srolovitz, David J.; Han, Jian
• 署名单位: City University of Hong Kong; Technische Universitat Dresden; Technische Universitat Dresden; University of Hong Kong
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-11428
• DOI: 10.1073/pnas.2310302121
• 发表日期: 2024-01-02
• 关键词: boundary motion; thin-films; GROWTH; crystal; mechanisms; plasticity; migration; DYNAMICS; mobility; metals

摘要

Grain rotation is commonly observed during the evolution of microstructures in polycrystalline materials of different kinds, including metals, ceramics, and colloidal crystals. It is widely accepted that interface migration in these systems is mediated by the motion of line defects with step and dislocation character, i.e., disconnections. We propose a crystallography-respecting continuum model for arbitrarily curved grain boundaries or heterophase interfaces, accounting for the disconnections' role in grain rotation. Numerical simulations demonstrate that changes in grain orientations, as well as interface morphology and internal stress field, are associated with disconnection flow. Our predictions agree with molecular dynamics simulation results for pure capillarity -driven evolution of grain boundaries and are interpreted through an extended Cahn- Taylor model. Significance Most materials made of inorganic solids are polycrystalline, including metals, ceramics, as well as many colloids and rocks. They consist of aggregates of misoriented grains separated by grain boundaries (GBs). While their evolution is classically based upon bubble/froth-like descriptions, grains are crystalline, not fluids: They are elastic solids, and relative crystallographic orientations play crucial roles. Microscopically, GB motion is mediated by disconnections, line defects possessing both step and dislocation character. Here, we introduce an approach to describe grain orientation changes during grain growth, an often-observed phenomenon not describable via classical capillarity-induced grain growth descriptions. We show that coupled GB migration via disconnection flow naturally leads to changes in grain orientation (crystallographic texture) and stress release.