Electron beam welding beam current on microstructure and mechanical properties of AISI 316 austenitic stainless steel

Welding experiments were carried out on AISI 316 austenitic stainless steel by vacuum electron beam welding (VEBW) machine at different welding beam currents (I-W = 70 mA, 80 mA, 90 mA and 100 mA). Different vacuum electron beam welding beam current on AISI 316 austenitic stainless steel microstructure and mechanical properties were analyzed by optical microscopy (OM), electron backscatter diffraction (EBSD) and mechanical stretching machines, combined with digital image correlation (DIC) stretching. The results show that the elongation and tensile strength of AISI 316 austenitic stainless steel increases and then decreases with the increase of I-W. The base material (BM) consists of fine austenite grains, while the weld material (WM) is characterized by fine equiaxed austenite grains scattered between elongated columnar austenite grains. No coarse austenite grains are observed in the heat affected zone (HAZ). The proper distribution of narrower HAZ and WM elongated columnar crystals ensures high yield strength (278 MPa), tensile strength (589 MPa) and good plasticity (88% total elongation) of the welded joints. The welded specimens are in ductile fracture mode and the fracture consists of various tough nests in different regions. The increase in elongation is attributed to the weakening of the thin lamellar grain structure and Cube texture {001} < 100 > formed byVEBW, which enhances the deformation coordination of dislocation slippage.