The role of grain boundary energy in grain boundary complexion transitions

[Display omitted] •Possible grain boundary energy versus temperature phenomena are reviewed.•Grain boundary energy measurements are reviewed.•Relationships among the grain boundary energy, character, and complexion are reviewed.•The importance of future studies of complexion transition kinetics is stressed. Recent findings about the role of the grain boundary energy in complexion transitions are reviewed. Grain boundary energy distributions are most commonly evaluated using measurements of grain boundary thermal grooves. The measurements demonstrate that when a stable high temperature complexion co-exists with a metastable low temperature complexion, the stable complexion has a lower energy. It has also been found that the changes in the grain boundary energy lead to changes in the grain boundary character distribution. Finally, recent experimental observations are consistent with the theoretical prediction that higher energy grain boundaries transform at lower temperatures than relatively lower energy grain boundaries. To better control microstructures developed through grain growth, it is necessary to learn more about the mechanism and kinetics of complexion transitions.