Dissolution and Coarsening Kinetics of γ′ Precipitates in Waspaloy during Solution Treatment at Temperatures of 1000-1045 °C

Dissolution and coarsening characteristics of γ′ precipitates in Waspaloy were investigated during solution treatments in the temperature range of 1000-1045 °C. The γ′ precipitates decreased significantly within 10 min and then remained unchanged. The dissolution behavior was quantitatively studied using the Johnson–Mehl–Avrami–Kolmogorov model. The dissolution activation energy that increased gradually with the increase in holding time was evaluated using the classical Arrhenius equation. For the sub-solvus heat-treated samples, the coarsening of the γ′ precipitates was observed after 10 min. A Lifshitz–Slyozov–Wagner (LSW)-type relationship was found to quantify the coarsening process. A γ′-coarsening activation energy that was comparable to the activation energy for the diffusion of Al and Ti in Ni was obtained based on the LSW model. This result verifies that the coarsening of the γ′ precipitates was mainly controlled by the matrix-diffusion of the γ′-forming elements. Abnormal grain growth was formed at 1030 °C due to the relatively low pinning force of the few γ′ precipitates. The present work contributes to the kinetics and mechanism of the evolution of the γ′ precipitates during the solution treatments and provides reference for optimizing the microstructure.