Experimental investigation and modeling of solute partition coefficients during directional solidification process of Al-1.5Cu-3Zn alloy

The solid-liquid interface of Al-1.5Cu-3Zn alloy with a temperature gradient of 80 K/cm was obtained by quenching with the liquid metal coolant (LMC) during directional solidification and the longitudinal section of the sample was examined by the optic microscope. The results show that the micromorphology of the sample solidified at a rate of 0.1 μm/s and 7.1 μm/s was observed to be the cellular growth interface and dendritic growth interface respectively. The distribution of Cu and Zn was measured and characterized by SEM with EDS and the equilibrium solute partition coefficients for Cu and Zn in Al-1.5Cu-3Zn alloy were calculated to be 0.31 and 0.58, respectively. These coefficients were further calculated using the activity model and concentration model, and the calculated partition coefficients for Cu and Zn in Al-Cu-Zn alloy by the two models were agreeable. The difference between the experimental data and the modeling result was discussed.