Microstructure and Mechanical Characterization of Friction-Stir-Welded 316L Austenitic Stainless Steels

Fusion welding of austenitic stainless steels (ASSs) causes undesirable metallographic changes. An attempt has been made to join 3-mm-thick 316L ASS plates using friction stir welding and correlate the microstructural evolution and the mechanical properties under various welding conditions. Tungsten alloy (W-Re) tool was employed for welding. Successful joints were obtained within a range of traverse speeds (45-85 mm/min) used in this work. Various zones were observed across the joint line. The stir zone exhibited considerable grain refinement and traces of delta ferrite phase. EBSD images showed a decreasing grain size with increased traverse speed. XRD patterns and TEM images confirmed the existence of delta ferrite. The mechanical properties of the joints including microhardness, tensile strength, impact toughness and bending were further reported.