Study on the Effect of Solution Treatment on Grain Growth Behavior of FGH96 Alloy Tube Billets

This paper systematically investigates the grain growth behavior of FGH96 alloy in the temperature range of 1130 °C to 1155 °C using characterization methods such as OM, SEM and EBSD. The results indicate that the grain size of the tube billet gradually increases with the rise in solution treatment temperature and the extension of holding time. During the solution treatment process, the γ′ phase formed, a large number of dispersed MC carbide particles distributed in the PPB region, and annealing twins all effectively pin the grain boundaries, thereby inhibiting grain growth and keeping the alloy grain size consistently below 18 μm. Based on the Arrhenius-type grain growth kinetics model, when the time exponent n=2, the coefficient of determination R2 reaches its maximum value (R2=0.89565), indicating the optimal fitting effect, and the error between the experimental values and the model predictions is minimized to only 30.15 %. During heat treatment, the extensive dissolution of γ′ phases and the uneven distribution of MC carbides and oxides along PPB weaken the local grain boundary pinning force. This provides favorable conditions for the preferential growth of partial grains, ultimately resulting in abnormally coarse grains and a mixed grain structure in the alloy.