Based on the microscopic phase-field model, the pre-aging temperature effects on the precipitation mechanism and microstructure evolution during two-step aging for Ni75Al9Cr16 alloy were simulated. The results show th...Based on the microscopic phase-field model, the pre-aging temperature effects on the precipitation mechanism and microstructure evolution during two-step aging for Ni75Al9Cr16 alloy were simulated. The results show that the early precipitation mechanism of L12 phase is the mixed mechanism of spinodal decomposition and non-classical nucleation growth, whereas the early precipitation mechanism of DO22 phase is spinodal decomposition when the pre-aging temperature is 873 K. The early precipitation mechanism of L12 phase is non-classical nucleation growth, whereas the early precipitation mechanism of DO22 phase is spinodal decomposition when the pre-aging temperature is 973 K. Under the effects of elastic strain energy, the cubic particles exhibit directional alignment along [100] and [010] directions during the late precipitation, which is more obvious at lower pre-temperature. DO22 phases appear earlier than L12 phases under these two kinds of precipitation processes; and the nucleation incubation time becomes long with the increase of pre-temperature.展开更多
（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 di...（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.展开更多
基金Project(50671084) supported by the National Natural Science Foundation of ChinaProject(Z200714) supported by the Postgraduate Foundation of Northwestern Polytechnical University, China
文摘Based on the microscopic phase-field model, the pre-aging temperature effects on the precipitation mechanism and microstructure evolution during two-step aging for Ni75Al9Cr16 alloy were simulated. The results show that the early precipitation mechanism of L12 phase is the mixed mechanism of spinodal decomposition and non-classical nucleation growth, whereas the early precipitation mechanism of DO22 phase is spinodal decomposition when the pre-aging temperature is 873 K. The early precipitation mechanism of L12 phase is non-classical nucleation growth, whereas the early precipitation mechanism of DO22 phase is spinodal decomposition when the pre-aging temperature is 973 K. Under the effects of elastic strain energy, the cubic particles exhibit directional alignment along [100] and [010] directions during the late precipitation, which is more obvious at lower pre-temperature. DO22 phases appear earlier than L12 phases under these two kinds of precipitation processes; and the nucleation incubation time becomes long with the increase of pre-temperature.
基金Projects (51021063,51301208) supported by the National Natural Science Foundation of ChinaProject (GZ755) supported by Sino-German Center for Promotion of Science+1 种基金Project (2011CB610401) supported by the National Basic Research Program of ChinaProject supported by Shenghua Scholar Program of Central South University,China
文摘（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.
