Site occupation evolution of alloying elements in L12 phase during phase transformation in Ni75Al7.5V17.5
(1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China;
2. Beijing Aeronautical Science and Technology Research Institute,
Commercial Aircraft Corporation of China Ltd., Beijing 100083, China)
2. Beijing Aeronautical Science and Technology Research Institute,
Commercial Aircraft Corporation of China Ltd., Beijing 100083, China)
Abstract: Correlation between site occupation evolution of alloying elements in L12 phase and growth of DO22 phase in Ni75Al7.5V17.5 was studied using microscopic phase field model. The results demonstrate that the growing process of DO22 phase can be divided into two stages. At the early stage, composition in the centre part of L12 phase almost remains unchanged, and the nucleation and growth of DO22 phase is controlled by the decrease of interface between L12 phases. At the late stage, part of V for growth of DO22 phase is supplied from the centre part of L12 phase and mainly comes from Al sublattice, the excess Ni spared from the decreasing L12 phase migrates into the centre part of L12 phase and occupies the Ni sublattices exclusively, while the excess Al mainly occupies the Al sublattice. At the late stage, the growth of DO22 phase is controlled by the evolution of antisite atoms and ternary additions in the centre part of L12 phase.
Key words: nickel based superalloys; Ni75Al7.5V17.5 alloy; phase, transformation; micro-phase field; grain growth; antisite defect