Solute migration and microstructure evolution of the hypereutectic Cu-73.4 wt% Ag alloy during directional solidification under high-gradient magnetic fields

During preparation of metallic material, solute migration has a significant effect on the microstructure. High magnetic field has an enormous potential on controlling alloy solidification on the basis of Lorentz force, magnetic force, etc. In this work, directional solidification experiments of a Cu-73.4 wt% Ag alloy have been conducted under different gradient magnetic fields. The effects of gradient magnetic fields on the solute migration and microstructure evolution of the alloys during the directional solidification process have been investigated. Without magnetic field, the alloy showed an aligned dendritic microstructure. Under a uniform magnetic field, the dendritic microstructure transformed to a eutectic morphology. Under a gradient magnetic field, the alloy exhibited again the dendritic microstructure, but with poor alignment. The transformation of the microstructure from aligned dendritic to eutectic to poor aligned dendritic morphology can be attributed to the combining effects of the Lorentz force and magnetic force on the migration of Cu solute at the solid/liquid interface. The results of this work provide a new insight to regulating the microstructure of alloys using high gradient magnetic fields.