Effect of Melt Overheating Treatment on the Melt Structure and Solidified Structures of Al75Bi9Sn16 Immiscible Alloy

In this paper, the liquid phase separation and solidification process of the Al75Bi9Sn16 immiscible alloy were studied with calorimetric and resistivity methods to make the melt superheated treatment process. The impact of melt overheating treatment (MOT) on the phase constitution and solidification microstructures were investigated using X-Ray diffraction (XRD) and field emission scanning electron microscope (FESEM) to determine the structural sensitivity to the melt superheated degree, and find a new strategy for improving the forming ability of the core-shell structure of the Al75Bi9Sn16 alloy. The results show that: the liquid phase separation and precipitation of primary (Sn) phase occur in 1039K-880K and 460K-403K; the core-shell structure with Sn-Bi-rich core and Al-rich shell can be formed under conventional casting conditions; the melt overheating treatment (MOT) can promote the formation of core-shell structure by increasing solidification time t0 and decreasing the average solidification rate v.