Effect of composition, high magnetic field and solidification parameters on eutectic morphology in Cu-Ag alloys: Eutectic modification by HMF and solidification

Abstract

High magnetic field (HMF) and solidification processes were changed during the solidification of both Cu-28 mass %Ag and Cu-72 mass %Ag alloys. The results indicated that the eutectic morphology in Cu-Ag alloys was affected by HMF, composition and solidification parameters. The lamellar spacing of Cu-28 mass %Ag alloy solidified by furnace-cooling was refined by the application of HMF owing to the decreased diffusion coefficient in mushy zone. The lamellar spacing in both Cu-28 mass %Ag sample held at the eutectic temperature and Cu-72 mass %Ag sample by slow controlling cooling was increased by HMF, which might be attributed to the dominated thermolectromagnetic convection. The lamellar spacing in Cu-72 mass %Ag alloys was increased compared with that of Cu-28 mass %Ag alloys because of the decreased growth rates. In Cu-28 mass %Ag alloy, however, fluid transverse velocity gradient was dominate rather than the growth rate and the imposition of HMF had reverse influences on the lamellar spacing. The lamellar-rod transition of Cu phase was promoted by HMF because of the increased Cu volume fraction in eutectic component. These results shed light on the dependence of eutectic morphology in Cu-Ag alloys on composition, external high magnetic field and solidification parameters.