Interaction of heating temperature and rate inducing abnormal grain growth in a novel Ti–Mo martensitic steel

A detailed comparative analysis of microstructure evolution, precipitate characteristics, and hardness was conducted on Ti-Mo martensitic steel subjected to reheating at varying temperatures and rates. Results indicate that the interaction between heating temperature and rate exerts critical control over microstructural development and the behavior of (Ti, Mo, Fe)C carbides during rapid heat treatment of Ti-Mo martensitic steel. The combination of elevated temperatures and high heating rate triggers abnormal grain growth (AGG), challenging the conventional paradigm that rapid heating universally refines grains and enhances strength-toughness. Furthermore, AGG initiation stems from the coupled effect of coarsened (Ti, Mo, Fe)C carbides and exponentially increased grain boundary mobility under high-temperature, rapid heating conditions. Additionally, the competitive kinetics between re-precipitation and coarsening of (Ti, Mo, Fe)C carbides are modulated by temperature-rate interactions. Re-precipitation dominates during high-temperature slow heating, whereas particle coarsening prevails under high-temperature rapid heating due to non-equilibrium dissolution effects.