Computer simulation of atomic ordering and compositional clustering in the pseudobinary Ni 3Al–Ni 3V system

Abstract

The kinetics of diffusional phase transformations in the pseudobinary Ni 3Al–Ni 3V system were studied using a computer simulation technique based on microscope diffusion equations. Our focus is on the initial stages of atomic ordering and compositional clustering process during the phase transformation of an initially homogeneous disordered f.c.c. ternary alloy (Ni 75Al 25− x V x ) into a two-phase mixture of L1 2 (Ni 3Al) and DO 22 (Ni 3V) ordered phases. A thermodynamic model is proposed to describe the phase equilibria in this pseudobinary system. Our computer simulations demonstrated that at small vanadium content, the L1 2 ordered domains appear first, followed by the nucleation of DO 22 ordered domains at the antiphase domain boundaries of L1 2, whereas at large vanadium content, precipitation of DO 22 precedes L1 2 domain formation. The simulation results are discussed employing the thermodynamic stability analysis. The ordering and clustering kinetics predicted from our computer simulation are consistent with recent experimental observations.