Grain refinement of Al–Cu alloy in low voltage pulsed magnetic field

The effect of a low voltage pulsed magnetic field (LVPMF) on grain refinement of Al–Cu alloy was investigated at different solidification stages. The cooling curve was also studied to investigate the grain refinement mechanism of LVPMF. The fine grains are obtained by applying the LVPMF during the nucleation stage. The LVPMF has no obvious influence on the solidification structure when it is applied during liquid phase stage or crystal growth stage. Application of LVPMF increases the nucleation temperature of the isomorphous transformation, and also decreases the recalescence magnitude of the alloy. The refining mechanism was proposed that the LVPMF provides extra energy for nucleation, which decreases the energy barrier and the critical radius for nucleation, leading to high nucleation rate and grain refinement.