Evaluation of mechanical properties of recycled stainless-steel chips and glass waste particle reinforced AA6061 composites via friction stir processing

This study develops hybrid aluminum matrix composites based on AA6061 reinforced with borosilicate glass waste (GW) and stainless-steel chips (SSCs) using friction stir processing (FSP). GW (<45 µm) and SSC (<200 µm) were incorporated at varying ratios to evaluate their effects on microstructure and mechanical properties. Microstructural analysis confirmed uniform particle distribution and grain refinement in hybrid composites. All reinforced samples exhibited higher hardness (82–107 BHN) than the unreinforced friction stir processed (FSPed) AA6061 (70.2 BHN), with a maximum increase of 52% for the 100 wt.% GW composite. While single-reinforcement composites showed reduced tensile strength (77–82 MPa), hybrid composites demonstrated improved performance. The 50 wt.% GW–50 wt.% SSC composite achieved the highest tensile strength of 139 MPa, representing a 17% improvement over the unreinforced alloy. Impact energy also increased, with a maximum value of 55.4 J for the 60 wt.% GW–40 wt.% SSC composite, corresponding to a 33.5% improvement over the unreinforced FSPed AA6061. Fracture surface analysis revealed predominantly ductile fracture modes in the optimally hybridized composites. These results demonstrate that hybridization of silica-rich industrial waste and metal chips via FSP provides an effective and sustainable route for tailoring the strength–ductility–toughness balance of AA6061 composites.