Reduction in Microsegregation in Al–Cu Alloy by Alternating Magnetic Field

The microsegregation behavior of the Al-4.5 wt%Cu alloy solidified at different cooling rates under the alternating magnetic field (AMF) was investigated. The experimental results showed that the amount of non-equilibrium eutectics in the interdendritic region decreased upon applying the AMF at the same cooling rate. The change in microsegregation could be explained quantificationally by the modifications of dendritic coarsening, solid-state back diffusion and convection in the AMF. The enhanced diffusivity in the solid owing to the AMF was beneficial for the improvement in microsegregation compared to the cases without an AMF. In contrast, the enhanced dendritic coarsening and forced convection in the AMF were found to aggravate the microsegregation level. Considering the contributions of the changes in above factors, an increase in solid diffusivity was found to be primarily responsible for the reduced microsegregation in the AMF. In addition, the microsegregation in the AMF was modeled using the analytical model developed by Voller. The calculated and experimental results were in reasonable agreement.