Investigation of Mechanical and Wear Behaviour of the Surface Composite AA5083/TiO2 at Varying Different Tool Pin Profiles in Cooling-Assisted Friction Stir Process

This study employed friction stir processing to fabricate surface composites by integrating TiO2 reinforcement into aluminum alloy 5083, useing varied tool pin profiles under dry, cooled conditions. Thermal, microstructural, mechanical, and tribological analyses were performed on the surface composites. The choice of a tool pin profile significantly influenced the outcomes by altering localized heating and material flow dynamics. For investigation, five pin geometries—threaded cylindrical, square, hexagonal, threaded tapered cylindrical, and tapered cylindrical—were tested with constant rotational and traverse speeds. Temperature profiles were varied, with a maximum of 369.41°C, reduced to 212.47°C with the threaded cylindrical tool under cooling. The tapered cylindrical tool, with cooling, achieved an 87.5% grain refinement. Surface composite microhardness increased by 20.65% compared to AA5083. The square pin profile yielded a maximum tensile strength of 157.19 MPa without compromising elongation. SEM analysis indicated ductile failure in the surface composites. Pin-on-disc testing revealed that the square-profiled composite had a low specific wear rate, attributed to a reduced coefficient of friction (0.36–0.39 vs. 0.44 for the base alloy), influenced by reinforcing particles. SEM examination confirmed the abrasion and adhesion wear mechanisms in the produced surface composites.