Predicting γ′-Phase Stability in Co-Based Superalloys*

The discovery of a cobalt-based γ/γ′-forming superalloy in 2006 inspired our computational investigation of the Co-Al-W system. We use the Moment Tensor Potentials (MTP) active-learning framework to predict the total energy, forces, and stresses for nearly 300,000 derivative superstructures in the Co-Al-W system. We report several new structures on the convex hull with the ordered L1₂-Co₃(Al, W) crystal structure, which may correspond to the experimentally discovered γ′ phase. Small additions of tantalum, titanium, and vanadium lower the formation enthalpy of the L1₂ structure, which could act as γ′ stabilizers at high temperature. While the total cost of the MTP analysis is about 1/1000^th the cost of a similar result using DFT, the difference between calculated and predicted results is less than 3 meV/atom. MTP can be used for high-throughput phase stability analysis for many kinds of materials, such as high-temperature superalloys, multi-principle element alloys, high-T_c magnetic materials, superhard materials, and electrochemical materials.