Mechanical properties and microstructural evolution of rheocast A356 semi-solid slurry prepared by annular electromagnetic stirring

Nowadays, having an effective technique in preparing semi-solid slurries for rheocasting process seems to be an essential requirement. In this study, semi-solid slurry of A356 aluminum alloy was prepared by three-phase annular electromagnetic stirring (A-EMS) technique under different conditions. The effects of stirring current, pouring temperature and stirring time on microstructural evolution, mean particle size, shape factor and solid fraction were investigated. The rheocasting process was carried out by using a drop weight setup and to inject the prepared semi-solid slurry in optimal conditions into the step-die cavity. The filling behavior and mechanical properties of parts were studied. Microstructural evolution showed that the best semi-solid slurry which had fine spherical particles with the average size of ∼27 µm and a shape factor of ∼0.8 was achieved at the stirring current of 70 A, melt pouring temperature of 670 °C, and stirring time of 30 s. Under these conditions, the step-die cavity was completely filled at die preheating temperature of 470 °C. The hardness increases by decreasing step thickness as well as die preheating temperature. Moreover, the tensile properties are improved at lower die preheating temperatures. The fracture surface, which consists of a complex topography, indicates a typical ductile fracture.