Interfacial Phase-like Transitions and Grain Boundary Phase Diagrams

Grain boundaries (GBs) can exhibit distinct interfacial structures [see, e.g., a recent perspective article: Science 368: 381 (2024)], which can be treated as 2D interfacial phases (also named as “complexions”). As bulk phase diagrams are arguably the most useful materials science tool, it is envisioned that their GB counterparts can be equally useful for materials design. In this talk, I will first review a series of our studies to compute the GB phase (complexion) diagrams [Interdisciplinary Materials 2: 137 (2023)]. Recent collaborative studies computed a GB lambda diagram to explain activated sintering of a refractory high-entropy alloy [Scripta Materialia 239: 115777 (2024)] and utilized disordered GBs in compositionally complex perovskite oxides to improve lithium-ion conduction [Matter 6: 2395 (2023) and J. Adv. Ceram. 14: 9221047 (2025)]. In addition to temperature and chemical potentials, an applied electric field can induce a GB transition electrochemically [Nature Communications 12: 2374 (2021)]. A recent study utilized electrochemically induced GB transitions to create graded microstructures and tailor microstructural evolution [Materials Today 73: 66 (2024) and unpublished results].