Energy studies of precipitation sequence in Ni₇₅Al₁₀Cr₁₅ alloy based on the phase field theory

Abstract

Based on the phase field theory, the phase precipitation sequence of Ni₇₅Al₁₀Cr₁₅ alloy and the free energy of each phase were studied. Moreover, the interatomic potentials of L1₀ phase, L1₂ phase and DO₂₂ phase changing with temperature and concentrations were computed through utilizing the interatomic potentials equations induced by Khachaturyan’s relational equations between the interatomic potentials and the long-range order (LRO) parameters. Results match preceding work and demonstrate that the phase precipitation sequence of Ni₇₅Al₁₀Cr₁₅ alloy is the disordered phase → L1₀ pre-precipitation phase → L1₂ equilibrium phase → L1₂+DO₂₂ equilibrium phase. Free energies of L1₀ pre-precipitation phase are higher and interatomic potentials are smaller than those of L1₂ equilibrium phase; therefore, it is concluded that L1₀ phase is unstable, and phase transformation would occur to L1₂ which is more stable; L1₂ phase precipitates earlier than DO₂₂ phase because L1₂’s interaction potentials are larger than DO₂₂’s.