Efficient fabrication of semisolid nondendritic Al alloy slurry with high quality

Abstract

Subjecting a normal mechanical vibration to a cooling slope plate, is a proposed method for preparing semisolid nondendritic slurry, named shear-vibration coupling sub-rapid solidification (SCS). Taking Al-8Si alloy as model material, the temperature field and distribution field of solid or liquid phase during SCS were simulated using COMSOL Multiphysics software to primarily choose the optimal processing parameters. Subsequently, the slurries were prepared with the parameters selected according to the simulation results and the microstructures of the slurries were experimentally investigated. Results indicate that the simulation results could provide a basis for roughly choosing the processing parameters, although the calculated solid fractions are always higher than the experimental ones. The processing parameters affect the primary grain size, shape factor and solid fraction mainly through altering the contact duration of melt on the plate, and thus affecting the cooling effect on the melt, nucleation rate, and grain dissociation and proliferation. Experiments with optimized processing parameters show that the primary grains in the slurry have an average size of about 32 µm and shape factor of 1.38, and are quite uniform, even at the highest pouring rate of 2.81 kg·s-1, the size and shape factor are about 46 µm and 1.7, respectively, which implies that the proposed SCS is a promising technology for efficient fabrication of high-quality Al slurry available for engineering applications.