Atomic mobilities in fcc Cu–Mn–Ni–Zn alloys and their characterizations of uphill diffusion and zero-flux plane phenomena

Abstract

Abstract An effective approach to establish the atomic mobility parameters of quaternary Cu-rich fcc Cu–Mn–Ni–Zn alloys is presented through assessments of the critically-reviewed experimental diffusivities available in the literature by means of DICTRA (DIffusion Controlled TRAnsformation) software. In the quaternary Cu-rich fcc Cu–Mn–Ni–Zn alloys, atomic mobilities in ternary fcc Cu–Mn–Ni and Cu–Ni–Zn boundary systems were directly taken from our previous work, while atomic mobilities in ternary fcc Cu–Mn–Zn boudnary system were assessed as a function of temperature and composition in this work. Since no experimental data were available, the atomic mobility database for fcc Ni–Mn–Zn alloys was not assessed but just directly extrapolated based on the three constituent binary alloys. Considering that the accurate quaternary interdiffusion coefficients were usually absent in the literature, atomic mobilities in fcc Cu–Mn–Ni–Zn alloys were extrapolated based on the assessed atomic mobilities in the 4 ternary boundary systems. On the basis of the obtained mobility parameters, simulations of a series of ternary and quaternary diffusion couple experiments were performed. The concentration profiles and the diffusion paths in diffusion couples were well reproduced by the presently obtained parameters. Furthermore, 3D views of the concentration profiles, diffusion fluxes, chemical potential and quaternary interdiffusion coefficients surfaces were calculated with the obtained atomic mobilities to analyze the uphill diffusion and zero-flux plane phenomenon in some quaternary diffusion couples. In addition, simple criteria for judging whether the uphill diffusion and/or zero-flux plane can occur are also proposed.