Effects of axial static magnetic field on columnar to equiaxed transition in directionally solidified low carbon steel

The effects of axial static magnetic field (ASMF) on the columnar-to-equiaxed transition (CET) in directionally solidified low carbon steel including peritectic reactions were investigated. Experimental results show that the dendrite morphology of this peritectic steel can be modified under ASMF. The increases of the magnetic field intensity and temperature gradient and the decrease of the growth speed can promote the CET. The columnar dendrites become equiaxed dendrites at a low growth speed. According to numerical simulations, a thermoelectric magnetic convection in the melts and a thermoelectric magnetic force acting on the secondary dendrite neck are induced by the interaction between a thermoelectric current and ASMF. The influence of ASMF on the CET covers the formation of the thermoelectric magnetic convection, transport of the fragments in the melts and detachment of dendritic side arms. In addition, the application of ASMF can extend the process window of equiaxed grains formed.