Effect of welding parameters on microstructure and mechanical properties of aluminum alloy AA6082-T6 friction stir spot welds

Abstract

Friction stir spot welding is an alternative joining technique for lightweight materials such as aluminum alloys. In this study, the influence of welding parameters, namely rotational speed, plunge depth, dwell time and travel speed, on weld microstructure and weld strength of friction stir spot welded AA6082-T6 aluminum alloy have been investigated. The joined samples were investigated by the methods of microstructural observations, microhardness tests, tensile shear tests and fractography. The hardness values of weld zone decreased significantly after FSSW process. Among the weld zones, HAZ showed the lowest hardness values. Higher rotational speed and lower travel speed led to the lower hardness values in the weld zone. The plunge depth and dwell time did not significantly affect the hardness values in the weld zone, except the SZ near TMAZ. Larger plunge depth and higher dwell time promoted higher hardness values in the SZ near TMAZ. The tensile test results showed that tensile shear load increased with increasing plunge depth and dwell time and with decreasing tool rotational speed and travel speed. The most effective welding parameter was found as dwell time. Higher rotational speed, higher plunge depth, higher dwell time and lower travel speed resulted in relatively ductile fracture.