Microstructural characterization and tensile behavior of friction stir processed AA6061/Al₂Cu cast aluminum matrix composites

Friction stir processing (FSP) has emerged as an effective secondary processing technique to improve the microstructure and properties of aluminum matrix composites (AMCs). Al/(0–15 wt.%) Al₂Cu AMCs were prepared by adding pure copper powder to molten aluminum and subjected to FSP. The microstructural changes before and after FSP were studied using OM, SEM, EBSD and TEM. Cast composites exhibited coarse grains, segregation, pores and large polygonal shape particles. The distribution of particles was rearranged into a homogeneous distribution after FSP. Casting defects such as pores were eliminated. The large Al₂Cu particles were broken into fine sized particles. The grain size reduced remarkably due to severe plastic deformation and the pinning effect of the reinforced particles. The density of dislocations increased considerably after FSP. The microstructural changes resulted in an improvement of tensile strength and ductility. The possible strengthening mechanisms were reported.