Influence of rotation speed and holding time on Al-7Si alloy cast through rapid slurry formation (RSF) technique

Abstract

The experimental investigation consisted of casting Al-7Si alloy by rapid slurry formation(RSF) technique. The RSF process is based on the enthalpy exchange between at least two alloy systems having different enthalpies, with the aim of forming a semi-solid metal slurry. Thus, slurry with 0.3 solid fraction was made by this process. Prior to starting the experiment 0.01 wt.% SiB was also added in the melt for additional grain refinement. Stirring speed was varied from 800 to 1800 rpm and for each experiment the samples were quenched in water at different time intervals; 0 min., 5 min., 10 min. and 15 min. It was observed that rapid heat extraction, nucleation and forced shearing action developed globular α-Al phase. It was also found that rotation speed, holding time and addition of Si-B grain refiner affected the average α-Al particle size. The coarsening of particles was experimentally investigated and also theoretically described by applying the LSW theory