Mechanical Behavior and Thermal Stability of Nanocrystalline Metallic Materials with Thick Grain Boundaries

Grain boundaries play an important role in governing the mechanical and physical properties of materials. Classical grain boundaries in crystalline materials typically have a thickness of 1–2 atomic layers. Thick grain boundaries are referred to as grain boundaries of interfacial phases in-between crystalline grains with a typical thickness of 1–10 nm. This unique interface endows metallic materials with remarkable mechanical behaviors and thermal stability. In this review, we summarize the deformation mechanisms in nanocrystalline metals with thick grain boundaries, focusing on strength enhancement and strength–ductility synergy. The thermal stability of nanocrystalline metals with thick grain boundaries is also discussed. We finally highlight the potential contribution of design strategies to the development of metallic materials with thick grain boundaries and potential approaches to further understanding the underlying mechanisms behind deformation and thermal stability.