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In this article, a 3D finite element based thermo-mechanical model for friction stir welding (FSW) of a marine-grade aluminium alloy 5083 is proposed. The model demonstrates the thermal evaluation and the distribution of residual stresses and strains under the variation of process variables. The temperature profile of the weld joint during the FSW process and the mechanical properties of the joints are also experimentally evaluated. The necessary calibration of the model for the correct implementation of the thermal loading, mechanical loading, and boundary conditions was performed using the experimental results. The model simulation and experimental results are analyses in view of the process-property correlation study. The residual stress was evaluated along, and across the weld, centreline referred as longitudinal and transverse residual stresses, respectively. The magnitude of longitudinal residual stress is noted 60-80% higher than that of the transverse direction. The longitudinal residual stress generated a tensile oval shaped stress region around the tool shoulder confined to a maximum distance of about 25mm from the axis of the tool along the weld line. It encompasses the weld-nugget to thermo-mechanically affected zone (TMAZ), while the parent metal region is mostly experiences the compressive residual stresses. However, the transverse residual stress region appears like wing shaped region spread out in both the advancing and retreating side of the weld and occupying approximately double the area as compared to the longitudinal residual stresses. Overall, the study revealed a corelation between the FSW process variables such as welding speed and the tool rotational speed with the residual stress and the mechanical properties of the joint.

The distribution of residual stresses across the joint interface of dissimilar joining between AA5083 and HSLA steel by friction stir welding technique was investigated through 2D XRD method and a numerical simulation model. The measured and simulated residual stress distributions are compared and discussed in the context of active recrystallisation mechanism and the possible presence of intermetallic compound (IMC) layers across the joint interface. The active dynamic recrystallisation (DRX) and multiple Fe/Al series IMCs as evident from the EBSD and 2D XRD, respectively critically demonstrated the variation in residual stresses between the experimental and theoretical values. The highest residual stress values of 375 and 281 MPa were recorded for the HSLA steel side and AA5083 side, respectively.

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