Experimental and numerical study of temperature and residual stress in two-pass friction stir welding of dissimilar alloys 6061-T6 to 5083

This investigation explores the friction stir welding of dissimilar AA6061-AA5083 aluminum alloy joints using experimental methods and numerical modeling techniques. The objective was to assess the effects of welding parameters on heat distribution and their impact on residual stress, microstructure, and hardness. To validate the model, a comparison was made between the simulation results and the experimental data. The modeling results and residual stress measurements obtained through the XRD method indicated that increasing the number of welding passes from one to two at a constant rotational speed of 1100 rpm, while reducing the tool traverse speed from 32 to 25 mm/min, led to an increase in the thermal gradient and residual stresses. An analysis of longitudinal and transverse residual stress values revealed a combination of tensile and compressive stresses. In single-pass welding, heat distribution was skewed toward the retreating side; however, altering the tool rotation direction in the second pass resulted in symmetrical heat distribution on both the advancing and retreating sides compared to the first pass. Moreover, increasing the number of welding passes from one to two at a rotational speed of 1100 rpm and a traverse speed of 25 mm/min resulted in a reduction of the average grain size across all microstructural regions and a 21% increase in hardness.