Progress in Interfacial Thermodynamics and Grain Boundary Complexion Diagram

Grain boundaries (GBs), a crucial component of microstructures, have a significant influence on the properties of materials. The GB complexion (GBC) transitions are essential information to accurately explain numerous material phenomena. However, owing to the complexity of GB structures and the difficulty in observation of GBC transitions, there is still no direct evidence and mechanism explanation for these material phenomena. With the advancement of characterization equipment, especially spherical aberration-correction transmission electron microscopy, coupled with powerful computer simulation, the establishment of interfacial thermodynamic models to construct different types of GBC diagrams, which provide a broad prospect for the study of GB structures and GBC transitions, is essential. In this paper, the progress of interface thermodynamics and GBC diagrams from the aspects of the classification and characterization of GBs and GBC transitions, interface thermodynamic models, and the construction of GBC diagrams were reviewed. The paper also looks forward to the future development of interface thermodynamics and GBC diagrams.