Tailoring the microstructure and properties of a Cu–Co immiscible alloy by high magnetic field assisted heat treatment

Abstract

The microstructure and properties of a Cu50Co50 immiscible alloy prepared by directional solidification were investigated experimentally via heat treatment assisted by a magnetic field of 10 T. The alloys were subjected to a heat treatment assisted high magnetic field in the solid state at 1070 °C and semi-solid state at 1300 °C for 6 h respectively. The results showed that in the solid state, with an applied high magnetic field, the fragmentation and refinement of the Co-rich dendrite phase can be ascribed to the reduction in the coarsening coefficient. In the semi-solid state, the refinement of dendrites was due to the melting of the dendrite outer shell. However, the fragmentation of dendrites and the deviation of the growth direction could be ascribed to the coupling effect of Lorentz, TEMF and TEMC, which changed the flow of the melt and affected solute migration. In both cases, the hardness of the Cu-rich matrix can be improved by imposing a high magnetic field. The variation in magnetic properties mainly relied on the decrease in the diamagnetic phase contribution and the change in alloy orientation under a high magnetic field. The current research initiates a novel method to tailor the microstructure and fabricate immiscible alloys with excellent properties via high magnetic field assisted heat treatment.