This study characterises the process-property relationship of Wire Arc Additive Manufacturing (WAAM) assisted by post-deposition Friction Stir Welding (FSW) for Aluminium Alloy 4043 (AA4043) deposited on an AA6061-T6 substrate. WAAM samples were fabricated using a robotic Gas Metal Arc Welding (GMAW) system, with deposition parameters (arc current, arc voltage, travel speed) optimised via a Taguchi L9 design of experiments, evaluating bead height and bead width as dual responses. The optimised WAAM parameter set (140 A, 20 V, 400 mm/min) was subsequently treated with post-deposition FSW (900 RPM, 30 mm/min) using a custom-fabricated jig. Microstructural evolution was evaluated using FE-SEM and EDX, while mechanical performance was assessed through Vickers microhardness testing. As-deposited WAAM samples exhibited coarse columnar α-Al dendrites, Mg2Si-rich eutectic segregation, and interlayer porosity, yielding a mean hardness of 66.3 HV. Post-deposition FSW induced dynamic recrystallisation, refining the microstructure into fine equiaxed grains, homogenising the Mg2Si-rich phase, and eliminating visible porosity, raising the mean hardness to 95.3 HV (an increase of approximately 44%). These findings indicate that post-deposition FSW is an effective post-processing strategy for mitigating the inherent defects of WAAM-fabricated AA4043 components, offering a viable pathway toward producing aluminium parts with superior structural integrity for aerospace, automotive, and marine applications.
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