Investigation of weld defects, microstructural, and mechanical features of TWIP and austenitic stainless steel dissimilar joints by pulsed GTAW process.

The herein study investigated defects, microstructure, and mechanical properties of two dissimilar welded joints between a twinning induced plasticity (TWIP) steel and the austenitic stainless steel (ASS) of grade AISI 304L. Dissimilar two-pass welded joints were performed through the pulsed gas tungsten arc welding (GTAW-P) process. Weld defects were characterized through radiographic testing, light optical (LOM), and scanning electron microscopy (SEM). Discontinuities (lack of fusion) formed in autogenous and filler metal joints were associated with distortion and uneven heat input distribution. Macrographs and radiograms of weld bead cross-section revealed that discontinuities were linear (in the autogenous weld) and rounded (in filler metal weld). The linear discontinuity induced hot cracking in the fusion zone (FZ). The energy-dispersive X-ray spectroscopy (EDS) line scanning performed on both dissimilar weldments indicated that the element diffusion process was produced from the base material (BM) to the FZ. The mechanical characterization demonstrated that the dissimilar welded joint with filler metal (ER309L-Si) had higher mechanical properties than the autogenous one. The Si addition to the welded metal and the heterogeneous grain size distribution in the TWIP steel side contributed to enhancing the mechanical strength and elongation to fracture. [ABSTRACT FROM AUTHOR]