Investigation on microstructure and mechanical properties of double-sided synchronous TIP TIG arc butt welded duplex stainless steel

Double-sided synchronous TIP TIG arc butt welding (DSSTTABW) is firstly carried out to join 5-mm SAF 2205 duplex stainless steel (DSS) plates without grooving. The microstructure and mechanical properties of DSSTTABW joints, including microhardness, transverse tension, and bend properties, are evaluated systematically. Results show that sound DSS joint, with excellent appearance and properties, can be obtained through the DSSTTABW process. In DSSTTABW joints, a deal of second austenite (γ2) appears in the weld metal, resulting in a slight increment of austenite volume fraction of the weld zone. Meanwhile sigma (σ) phase precipitates at the grain boundaries of delta ferrite (δ-Fe) and austenite of the weld zone. Mechanical property tests show that the DSSTTABW weldment exhibits higher tensile strength and microhardness but lower ductility compared to 2205 DSS base metal due to the existing Widmänstten-type austenite (WA) and σ phase. All weldments fracture at the weld zones in the mode of ductile. After bending tests, no surface cracks are observed on the DSSTTABW joint.