Modification of tribological and mechanical properties by a novel tool during friction stir processing of ZrO2+TiN particle reinforced AZ31 Mg alloy

In this study, surface Mg-based composites reinforced by adding ZrO₂ and TiN were developed through Friction Stir Processing (FSP) using both a conventional (CCP) and a newly modified tool (PCP). Microstructural analysis indicated a more effective grain refinement achieved by employing the PCP tool, resulting in a finer and equiaxed grain structure with approximately a 20 % reduction in average grain size compared to the CCP-treated composite. Furthermore, a more uniform distribution of particles with reduced agglomeration was achieved after using the PCP tool. Significant enhancements in mechanical properties, including shear strength and microhardness, were observed in the composite processed by the PCP tool, to the extent that an approximate increase of 15 % in mean microhardness values was recorded compared to the composite processed by the CCP tool. Additionally, the use of the PCP tool resulted in an improvement in the composite's shear strength and formability, with the shear strength of the PCP-treated composite reaching approximately 196 MPa, compared to around 161 MPa for the CCP-treated composite. Additionally, the coefficient of friction decreased from approximately 0.39 in the CCP-treated composite to approximately 0.33 in the PCP-treated composite, which aligns reliably with the wear rate and weight loss results.