Dissolution controlled grain growth in Nickel Alloy UDIMET 720Li

The present paper examines the mechanisms for simultaneous manipulation of grain size and gamma ' dissolution leading to the microstructure that balance creep and fatigue properties in UDIMET 720Li. For sub (near) solvus heat treatments, grain growth and gamma ' dissolution occur simultaneously. Grain size following heat treatment is determined largely by the primary gamma ' particle dispersion, via Zener-Smith pinning. Remarkably, grain growth occurs only as a result of precipitate dissolution. The resulting grain size is dictated by a combination of initial particle dispersion in the as-received material and heat treatment temperature. It is likely to hold so long as the initial grain size is close to the Zener-Smith limit and where the kinetics of grain growth and dissolution share similar rates.