Effect of SiC/Si3N4 micro-reinforcement on mechanical and wear properties of friction stir welded AA6061-T6 aluminum alloy

Friction stir welding (FSW) is extensively used to join aluminum alloys components for applications in structural, aviation and automotive sectors. In this investigation, the mechanical properties (tensile strength, percentage elongation, and microhardness), abrasive wear properties and microstructure of friction stir welded joint of AA6061-T6 were studied by inter-plate reinforcing of silicon carbide microparticles (mu SiC) and silicon nitride microparticles (mu Si3N4). The friction stir welding was performed at different tool rotational speed (TRS) (750, 1000 and 1400 rpm) and welding speed of 56, 80 and 112 mm/min. The friction stir welded joint without reinforcement and with mu SiC exhibited maximum tensile strength at two combinations of welding speed and tool rotational speed; one at welding speed of 112 mm/min, TRS of 1000 RPM and other at welding speed of 56 mm/min and TRS of 1400 rpm. It was realized that the reinforcement of mu SiC and mu Si3N4 decreased the tensile properties of the welded joint but improved the abrasive wear and microhardness properties considerably in the stir zone. The reinforcement of mu SiC during FSW demonstrated better tensile, microhardness and abrasive wear resistant properties than the FSW joints with mu Si3N4 reinforcement. The improvement in microhardness of the FSW joint reinforced with SiC and Si3N4 microparticles is attributed to the pinning effect produced by the hard particles inclusions.