Effect of an ER4043 filler on the microstructural evolution and mechanical/ nanomechanical performance of dissimilar AA-6061-LF-06 pulsed TIG weldments

In the present study, AA-6061 and LF-06 aluminum alloys were subjected to pulsed Tungsten Inert Gas (P-TIG) welding using ER4043 (Al-Si) Filler alloy. A detailed microstructural examination revealed significant variations in the grain morphology, accompanied by the formation of intermetallic phases, notably Mg ₂ Si, Al ₃ Mg ₂ , and Al ₃ Fe, as well as the presence of both columnar and equiaxed grains. X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analyses corroborated the identification of peaks corresponding to second-phase precipitates Mg ₂ Si, Al ₃ Mg ₂ , and Al ₃ Fe within the fusion zone (FZ). Notably, the welded joint exhibited no signs of porosity or hot cracking. Microhardness and nanohardness assessments demonstrated a significant increase in hardness, approximately 68% and 51% higher in the FZ compared to the AA-6061 base alloy, respectively. Furthermore, tensile test results indicated that the weldment strength of 132 MPa corresponds to ∼95% of the AA-6061 base alloy strength (139 MPa). AFM analysis demonstrated moderate pile-up behavior in the FZ compared to the base alloys, indicating localized plastic accommodation associated with microstructural heterogeneity and second-phase particles, without adversely affecting joint integrity.