Processing-structure-property correlation in nano-SiC-reinforced friction stir welded aluminum joints

In this work, friction stir welding (FSW) of AA5086-H34 aluminum with nano-sized SiC reinforcement is performed. The effects of traverse and rotational speeds and number of passes on microstructure, hardness, and tensile behavior of the FSWed joints are studied. Single-pass FSWed specimens containing reinforcements represented SiC particle-rich and SiC particle-free regions in grain refined Al-matrix within the stir zone (SZ), which could be affected by changing traverse and rotational speeds. Multi-pass FSW led to more grain refinement and homogenous distribution of SiC particles. Hardness measurement revealed that both single- and multi-pass FSW with SiC particles increased hardness values. Furthermore, tensile tests demonstrated that single-pass FSWed specimens with SiC possessed lower tensile strength and percentage of elongation in comparison to as-received aluminum and showed brittle fracture in the stir zone, while a remarkable increase in tensile properties was observed for multi-pass FSWed specimens with SiC particles and consequent ductile fracture in base metal.