In this study, friction stir welding of AA2014-O and AA2014-T6 aluminum alloy was performed at various welding speeds to evaluate the influence of temper conditions of base metal on the properties of the welded joints. The results showed strong influence of base metal temper conditions on the microstructural morphologies and mechanical behavior of the welded joints. In the 2014-O joints, different zones of weld joint were diffused into each other and there was no clear interface between them. In 2014-T6 joints, there was a distinct demarcation between the NZ, TMAZ, HAZ and base metal. The welded joints in 2014-O temper condition showed increase in hardness in the vicinity of weld center due to grain refinement whereas, in 2014-T6, softening occurred in the same region by the dissolution of strengthening precipitates. The mechanical properties of 2014-O joints were equivalent to the base metal showing a 100% weld efficiency with fracture located in the base metal, whereas 2014-T6 welds exhibited about 70% weld efficiency with fracture located at the NZ/TMAZ interface. All the samples in mechanical testing fractured at retreating side (RS) which exhibited heterogeneity in the mechanical properties of the welded joints. SEM fractographic analysis revealed a ductile fracture mode comprising of dimples in both temper conditions. The size and shape of the dimples was strongly dependent on base metal temper condition.

In this study, friction stir welding of AA2014-O and AA2014-T6 aluminum alloy was performed at various welding speeds to evaluate the in uence of temper conditions of base metal on the properties of the welded joints. The results showed strong in uence of base metal temper conditions on the microstructural morphologies and mechanical behavior of the welded joints. In the 2014-O joints, different zones of weld joint were diffused into each other and there was no clear interface between them. In 2014-T6 joints, there was a distinct demarcation between the NZ, TMAZ, HAZ and base metal. The welded joints in 2014-O temper condition showed increase in hardness in the vicinity of weld center due to grain re nement whereas, in 2014-T6, softening occurred in the same region by the dissolution of strengthening precipitates. The mechanical properties of 2014-O joints were equivalent to the base metal showing a 100% weld e ciency with fracture located in the base metal, whereas 2014-T6 welds exhibited about 70% weld e ciency with fracture located at the NZ/TMAZ interface. All the samples in mechanical testing fractured at retreating side (RS) which exhibited heterogeneity in the mechanical properties of the welded joints. SEM fractographic analysis revealed a ductile fracture mode comprising of dimples in both temper conditions. The size and shape of the dimples was strongly dependent on base metal temper condition.

In this study, the Taguchi Design of Experiment method was used to determine the optimal Friction Stir Welding (FSW) parameters for improving the mechanical properties of AA 2014-T6 alloy butt joints. The three most significant parameters-tool rotational speed, tool linear travel speed and tool tilt angle-were optimized using the L9 orthogonal array design. The optimal welding parameters for the maximum tensile strength were determined by analyzing the signal-to-noise (S/N) ratio. A regression model was developed for the desired responses. The optimal tensile strength was achieved at the 1000 rpm, rotational speed, 600 mm/rev welding speed, and 2 ° tool title angle. The results were confirmed using a steady-state heat transfer model generated from the COMSOL Multiphysics Finite Element software. The identified optimal conditions were verified by experimental validation tests. The experimental results were consistent with the predicted values. Analysis of variance (ANOVA) was conducted to determine the effects of individual parameters and to identify the most significant process parameter. ANOVA indicated that the most significant factor affecting the mechanical behavior of the joint was the tool rotation speed followed by the linear travel speed.