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

Based on the phase field theory, the phase precipitation sequence of NiAlCr alloy and the free energy of each phase were studied. Moreover, the interatomic potentials of L1 phase, L1 phase and DO 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 NiAlCr alloy is the disordered phase → L1 pre-precipitation phase → L1 equilibrium phase → L1+DO equilibrium phase. Free energies of L1 pre-precipitation phase are higher and interatomic potentials are smaller than those of L1 equilibrium phase; therefore, it is concluded that L1 phase is unstable, and phase transformation would occur to L1 which is more stable; L1 phase precipitates earlier than DO phase because L1's interaction potentials are larger than DO's. [ABSTRACT FROM AUTHOR]