Enhanced mechanical and microstructural properties of 2205 duplex stainless steel welded using autogenous gas tungsten arc welding

ABSTRACT This study examines the mechanical and microstructural characteristics of 2205 duplex stainless steel (DSS) sheets welded using Autogenous Gas Tungsten Arc Welding (A-GTAW) under optimized conditions. A 2 mm thick DSS plate was butt-welded using a welding current of 100 A, an arc length of 2.4 mm, and a welding speed of 250 mm/s. The welded joint was evaluated for tensile strength, hardness, ductility, bending performance, and formability. The joint exhibited an ultimate tensile strength of 705 MPa, representing a 34% improvement over the base metal (BM), with an elongation of 56.5%. Bending tests confirmed that the joint maintained its structural integrity under severe plastic deformation, with an r/t bending ratio of 2, demonstrating excellent ductility. Microhardness measurements showed a 12.5% increase in hardness in the fusion zone (FZ) relative to the BM, attributed to δ-ferrite and γ-austenite phase transformations. The microstructural analysis revealed the formation of Widmanstätten austenite (WiA), secondary austenite (SA), and partially transformed austenite (PTA) in the FZ, with quantified phase percentages contributing to the enhanced mechanical properties. Fractographic analysis identified ductile failure characterized by dimples, microvoid coalescence, and secondary cracks. The stress-strain curve exhibited a second jump, attributed to strain hardening effects in the welded joint. The Erichsen formability index increased by 10%, indicating superior forming behavior. These results demonstrate that A-GTAW, when applied under carefully controlled parameters, significantly enhances the mechanical performance and structural reliability of 2205 DSS joints, making it a viable technique for critical industrial applications requiring high strength, ductility, and corrosion resistance.