Effect of Al: W value on the precipitation process of Co-Al-W alloy: A phase-field study

Abstract

The microstructure evolution of Co-10Al-xW (x=8, 10, 12) alloys at different Al: W values was simulated based on the microscopic phase field dynamics model. The results show that: the Al: W value affects the γ′ phase precipitation mechanism of Co-Al-W alloy. When Al: W>1, the precipitation mechanism of γ′ phase of Co-10Al-8 W alloy is non-classical nucleation and growth mechanism. When Al: W=1, the γ′ phase precipitation mechanism of Co-10Al-10 W alloy is a mixture of non-classical nucleation and growth mechanism and instability decomposition mechanism, meanwhile, the formation time of γ/γ′ stable microstructure morphology is the shortest, and the stability of γ′ ordered phase is stronger. When Al: W<1, the γ′ phase precipitation mechanism of Co-10Al-12 W alloy is a mixed mechanism of equal component ordering and instability decomposition mechanism. Under different Al: W values, the γ′ precipitate phase of Co-Al-W alloy has similar stable micromorphology in the late precipitation stage, and all of them show square blocks along the direction of [001] and [100]. The main antisite defects in Co-Al-W alloys are AlCo and CoAl defects, and the influence of Al: W value on the antisite defects at different sites is different.