Semi-Solid Forming of A356 Alloy by Rapid Slurry Forming Process

Abstract

Rapid Slurry Forming (RSF) is a relatively new technique of semi-solid forming. RSF process has been used for A356, A356+Ti+B (grain refiner) and A356+Ti+B+Sr (grain refiner and modifier) Al alloys in the present investigation. All the three alloys were held at 597°C, at which about 30% solid fraction is obtained in the semi-solid slurry, for 0, 5, 10 and 15 minutes. After each holding time, the slurry was quenched in water to preserve the semi-solid microstructure. Microstructure of all the three alloys at each stage was examined and hardness was measured. A globular microstructure was obtained for the RSF-processed alloys. The globularity of-grains increased but grain size also increased and hardness decreased with increase in holding time. The optimum hold time appeared to be 5 minutes. The grain refiner and modifier did not seem to have any effect on the formation of semi solid slurry. The coarsening-grains was found to be faster than that predicted by the LSW theory.