Effect of Heat Treatments on the Microstructural Evolution of a Single Crystal High-Entropy Superalloy

The effect of solution heat treatment as well as primary and secondary aging treatment conditions on the microstructural evolution of a high-entropy superalloy was investigated. The as-cast sample shows coarsened γ′ precipitates and other extra phases at interdendrite region due to microsegregation. This microsegregation makes γ′ solvus unclear and decreases the solidus. After conducting the solution treatment determined in this study, primary aging conditions showing an aligned cubic γ′ phase at 1050 °C for 4 h and random spherical γ′ precipitates at 950 °C for 20 h in similar size were found. By using both samples, secondary aging conditions showing coarsened secondary γ′ precipitates and γ particles inside the γ′ precipitates at 800 °C for 20 h and fine secondary γ′ precipitates at 850 and 870 °C for 20 h were found.