Friction Stir Processing: Effect on Microstructure and Mechanical Properties in Cast Aluminum Alloys

Microstructural and mechanical data from the literature of friction stir processed (FSPed) cast aluminum alloys were reanalyzed. Results indicated that friction stir processing (FSP) produced more homogeneous microstructures, with finer eutectic Si particles, grains, and intermetallics. However, a relationship between microstructural measures and process parameters could not be established. Regardless of the resultant microstructure, structural casting defects, i.e., pores and oxide films, were reduced in size or completely eliminated after FSP. Consequently, ductility and fatigue life were drastically improved by FSP. Quality index analysis showed that some FSPed specimens have a higher structural quality than aerospace and premium quality castings, and can be used to determine the intrinsic properties of cast aluminum alloys.