Effect of Friction Stir Processing on Spray Formed Al-Si Alloy

In this study, Al-Si-Gr composites for cylinder liner application were synthesized using a spray forming technique to improve its wear resistance. The processing of these composites by the conventional casting routes is complicated due to liquid immiscibility and floating of low-density graphite powder during melt solidification. In the present investigation, Al-Si-Gr composite is produced by spray forming, and then friction stir processing (FSP) was introduced to refine the microstructure of spray formed composite. The current research work aims to study the Al-Si alloy using graphite and examine the changes produced in microstructure and mechanical properties of the material after FSP. Disc shape spray deposit castings were made of Al-6Si-5Gr, Al-12Si-5Gr and Al-18Si-5Gr composite. In addition to that, spray formed Al-Si-Gr composites were subjected to the FSP. The microstructure of the stir zone was observed to be highly refined compared to the spray formed material. FSP resulted in complete homogenization and elimination of casting defects, especially porosity. Mechanical properties like hardness and tensile strength were sharply improved after FSP.