Effect of a high-gradient magnetic field on grain refinement of a hypoeutectic Mn–Sb alloy during directional solidification

The obvious grain refinement of the primary MnSb phase has been observed in the Mn–89.7 wt% Sb alloy directionally solidified under a high-gradient magnetic field. With the application of a high-gradient magnetic field, the morphology of the primary MnSb phase transformed from developed dendritic-like to equiaxed-like, and the grain size decreased by approximately 93%. Refinement of the primary MnSb phase can be attributed to the constituent supercooling in front of the solidification interface, which promoted nucleation of the primary MnSb phase. The constituent supercooling can be linked to the enrichment of the Mn solute induced by the magnetic force and the Lorentz force that drove Mn solute migration and suppressed convection.