Regular γ/γ′ phase interface instability in a binary model nickel-based single-crystal alloy

In this paper, long-term thermal treatment of a binary Ni-Al model nickel-based superalloy was performed at 1000 °C for 50 h, 100 h and 200 h. The evolution of the γ/γ′ interface was studied. As the treatment time increased, the γ′ precipitates coarsened and grew. Regular interface instability was observed that the shape of the γ/γ′ interface changed from flat to wavy. This interfacial instability was caused by the dynamic balance of strain energy and surface energy at the interface between the two phases. In addition, secondary γ′ precipitates were observed after long-term treatment and some of the larger ones took on pillow-like shapes. The pillow-shaped distortion was because that the growth rate of the cube vertices was faster than that of other locations due to the different strain states at different locations.