Effect of liquid diffusion coefficients on microstructure evolution during solidification of Al356.1 alloy
(1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
2. Sino-German Cooperation Group “Microstructure in Al alloys”, Central South University, Changsha 410083, China)
2. Sino-German Cooperation Group “Microstructure in Al alloys”, Central South University, Changsha 410083, China)
Abstract: The effect of liquid diffusion coefficients on the microstructure evolution during solidification of primary (Al) phase in Al356.1 alloy was investigated by means of the phase-field simulation using two sets of diffusion coefficients in liquid phase, while fixing other thermophysical and numerical parameters. The first set is only with impurity coefficients of liquid phase in Arrhenius formula representing only the temperature dependence. While the second set is with the well-established atomic mobility database representing both temperature and concentration dependence. For the second set of liquid diffusion coefficients, the effect of non-diagonal diffusion coefficients on the microstructure evolution in Al356.1 alloy during solidification was also analyzed. The differences were observed in the morphology, tip velocity and composition profile ahead of the tip of the dendrite due to the three cases of liquid diffusivities. The simulation results indicate that accurate databases of mobilities in the liquid phase are highly needed for the quantitative simulation of microstructural evolution during solidification.
Key words: Al356.1 alloy; solidification; microstructure evolution; diffusion coefficient; phase-field simulation