Phase field model was employed to study the variations of interatomic potentials of Ni 3 Al (L1 2 phase) and Ni 3 V (DO 22 phase) as a function of temperature and concentration. The long-range order (LRO) parameter related interatomic potentials equations formulated by Khachaturyan were utilized to establish the inversion equations for L1 2 and DO 22 phases, with which interatomic potentials could be calculated. The interatomic potentials of Ni-Al and Ni-V exhibited approximately linear increases and decreases, individually, with enhanced Al concentration. Substituting the inverted interatomic potentials into the microscopic phase field equations led to three cases of precipitation sequence: the DO 22 phase preceded L1 2 phase precipitating at the interatomic potentials of Ni-V > Ni-Al; the vice cases; and two phases precipitated simultaneously at interatomic potentials of Ni-V and Ni-Al were equal.
DONG WeiPing WANG YongXin YANG Kun CHEN Zheng LU YanLi
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 →L 12 equilibrium phase →L 12+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.
