Experimental and Numerical Investigations of the Multi-scale Thermoelectromagnetic Convection on the Microstructure during Directionally Solidified Sn-5wt%Pb Alloys

摘要

In this paper, the effect of multi-scale thermoelectromagnetic convection (TEMC) on the microstructure in directionally solidified Sn-5wt%Pb alloys under a transverse magnetic field was studied experimentally and numerically. The experiments are conducted within sample diameters ranging from 0.8 to 12 mm and with various magnetic field intensities. Experimental results show that the transverse magnetic field tilts solid/liquid interface shape and causes the channel segregation. The sloping degree first increases to a maximum value at a critical magnetic field intensity (Bmax), and then decreases with the increase of the magnetic field intensity. The critical magnetic field intensity (Bmax) decreases with the increase of sample diameter. Finite-element modeling is performed to simulate the multi-scale TEMC by using COMSOL software. Numerical results indicate that the value of the TEMC increases to a maximum and then decreases with the increase of the magnetic field intensity. The tendency of the simulated TEMC agrees with the evolution process of solid/liquid interface morphology by experimental results. The inter-dendritic TEMC increases monotonically with the increasing of magnetic field intensity in the present study (B < 2 T). The modification of the solid/liquid interface and the channel segregation under the magnetic field should be attributed to the TEMC at the sample and inter-dendritic scales, respectively.