Microstructure and mechanical properties of S32001 duplex stainless steel TIG joints

With the low nickel duplex stainless steel S32001 as the research object, the tungsten inert gas welding(TIG) was used for automatic welding. The effects of different welding process parameters on the microstructure and phase composition of the joint were investigated, and the relationship between microstructure and mechanical properties was studied. The results have shown that under different welding process parameters, the surface of the welded joint is well formed. The microstructure is composed of austenite phase and ferrite phase, and the secondary austenite phase is precipitated at the boundary between the ferrite and the ferrite/austenite phase in the weld. The hardness of the joint presents a “W” shaped distribution, and the microhardness of the base metal(BM) is slightly higher, while the microhardness of the heat-affected zone(HAZ) is slightly lower. With the increase of heat input at the welded joint, the grain size in the weld area increases, the hardness value decreases, and the tensile strength and elongation after fracture of the specimen show a decreasing trend. The microhardness and tensile strength of the W₁ group were the highest, which were 254.1 HV ± 5.7 HV and 702.3 MPa, respectively. The fracture of the tensile specimen is composed of facets, micropores, and tear ridges, and some micron-scale inclusions can be observed. The weld is characterized by quasi-cleavage fracture.