A comprehensive investigation on various welding facets for FSW of advanced structural AMC

Abstract

The study comprehensively explores various welding facets for FSW of advanced structural AMC (AA6092/17.5 SiCp-T6) by varying the Tool Rotational Speed (TRS). Thermal variations, force-torque distribution, structural evolution, and joint mechanical characteristics were evaluated. At 1000 rpm, welding temperature increases along the welding direction, contrasting with other TRS. The cooling rate escalates as welding progresses. The temperature gap between the Advancing Side (AS) and the Retreating Side (RS) widens with higher TRS. Increasing TRS leads to decreased spindle torque and Z-force, with X-force fluctuations evident at lower TRS. Additionally, the TRP exhibits a direct linear relationship with the energy input during the welding process. Microstructural analysis reveals diverse SiC particle aggregation in the Nugget Zone (NZ) across all the TRS conditions. Notably, at 1500 rpm, an onion ring width of 80 µm is observed. At 1750 rpm, iron particles indicating tool wear and an Al2O3 mud-cake-like formation is traced out. Furthermore, as TRS rises to 1500 rpm, there is a decrease in the particle size, succeeded by an increase, aligning with variations in the grain size. Welds display lower hardness than the BM, following a 'W' shape profile with the AS-HAZ region consistently showing the lowest hardness across all conditions. Hardness peaks at 1500 rpm, then decreases. The Tensile samples mostly fracture outside the weld zone, except at 1700 rpm. UTS values range from 308 MPa to 358 MPa, with joint efficiency peaking at 87% for 1500 rpm before decreasing to 74%. Welding at 1500 rpm exhibits greater elongation compared to the Base Metal, with fractographic analysis indicating predominantly ductile failure, except at 1750 rpm, displaying a mixed mode of failure.