Study on Grain Growth and Grain Boundary Evolution of 740H Nickel‐Based Alloys under Different Solution Treatment Conditions.

This research examines the grain growth, microstructural characteristics, and grain boundary evolution of 740H nickel‐based alloy subjected to solution treatment following hot rolling. The results demonstrate that increasing the solution temperature and extending the holding time promote grain growth. A two‐stage grain growth model is developed, achieving a correlation coefficient of 0.979 and an average absolute relative error of 9.5%. The volume fraction of Σ3 grain boundaries initially increases and then decreases, peaking at 1150 °C under constant holding time. At a solution temperature of 1150 °C and a holding time of 60 min, the proportion of special grain boundaries in the sample reaches a maximum of 61.1%, with Σ3 grain boundaries comprising the majority at 59.8%. Their morphology progressively evolves into long, straight double Σ3 grain boundaries, and the distribution of grain boundary clusters becomes increasingly concentrated. Grain boundary engineering analysis reveals that during grain growth, twins gradually form and proliferate, dislocation recovery in the alloy is enhanced, and residual stress is progressively reduced. Under the conditions of 1150 °C solution temperature and 60 min holding time, grain boundary regulation performance is optimized, establishing this as the most effective heat treatment process. [ABSTRACT FROM AUTHOR]