Enhancement of hardness and wear strength of pure Cu and Cu–TiO2 composites via a friction stir process while maintaining electrical resistivity

The study aims to enhance the hardness and wear of copper and Cu–TiO2-based composites while maintaining high electrical conductivity through friction stir processing (FSP). It assesses the impact of TiO2 volume fractions and groove widths (GWs) on the wear, hardness, resistivity, and microstructure of FSPed Cu and FSPed Cu–TiO2 surface composite. The samples obtained from the stir zone showed an increase in microhardness of the Cu–TiO2 surface composite due to particle refinement, uniform distribution, and efficient sticking of TiO2 with Cu. Furthermore, the wear rate increased with decreasing TiO2 volume fractions in the composite. The worn surface microstructural analysis indicated a transition from harsh to gentle wear with increasing TiO2 volume fractions and GWs. The average grain size reduced significantly in reinforced stir zones compared to pure Cu, and particle size decreased further with increasing groove size. Hardness increased by 25 and 50% compared to unprocessed Cu, but only a negligible increase in electrical resistivity (2.3% Ωm) after FSP.