Cooling-Induced Improvements: Grain Refinement, Microstructural Evolution, and Mechanical Property Enhancement in Friction Stir Processed AA6063

This current study provides a thorough examination of the significant influence of natural and dry ice cooling on the microstructural characteristics and mechanical properties of friction stir processed (FSPed) AA6063 alloys. The FSPed samples, exposed to different cooling conditions, underwent detailed scrutiny to unveil intricate details regarding grain refinement, precipitation behavior, microhardness, tensile strength, ductility, and tensile fracture characteristics. Microstructural analysis reveals that natural cooling results in a gradual evolution of the microstructure characterized by a fine-grained structure (9.2 µm). Conversely, dry ice cooling induces rapid cooling, leading to further grain refinement (7 µm). Natural cooling achieves a balance between strength (296 MPa) and ductility (23.9%), whereas dry ice cooling enhances strength (274 MPa) while sacrificing some ductility (23.4%). The influence of cooling conditions on the tensile fracture characteristics is elucidated, providing insights into the alloys’ ductility and fracture resistance. Significant variations in mechanical properties are observed. Natural cooling yields a balanced enhancement, with an 18.6% increase in microhardness, a 17.6% rise in strength, and a commendable 26.4% improvement in elongation. Conversely, dry ice cooling leads to a substantial 25.6% increase in hardness, an impressive 27% surge in tensile strength, and a moderate 23.8% enhancement in elongation.