Effect of Cu/Mg Solute Combined with Ultrasonic Melt Treatment on Microstructural Refinement of Hypoeutectic Al-7Si-Cu-Mg Alloys

摘要

It is well known that ultrasonic melt treatment (UST) affects not only the niicrostructural refinement but also the microsegregation. Our recent study1' revealed that the solid-state diffusion of Cu effectively occurred along a-Al dendrites of which the arm spacings were significantly reduced by UST, reducing the overall volume fraction of Cu-rich intermetallics formed in the final stage of solidification. In the early stage of solidification, solute segregation ahead of solid-liquid interface can also induce constitutional supercooling (CS) in the early stage of solidification and thus affect the grain refinement. The exact role of solute in the grain refinement under UST has received little attention and hence has not been yet fully understood. Therefore, this work aimed to investigate the combined effects of Cu/Mg solute and UST on the grain refinement of a hypoeutectic Al-7Si-Cu-Mg alloy.