Microstructural evolution and enhanced mechanical performance of dissimilar CoCrFeMnNi high entropy alloy-duplex stainless steel welds using laser beam welding

In this study, dissimilar welding of high entropy alloys (HEAs) and duplex stainless steel (DSS) was performed using laser beam welding. The work investigates the microstructure, tensile properties, and fracture behavior of the welded joints between CoCrFeMnNi HEA and DSS. Detailed microstructural characterization using SEM, EBSD, and XRD revealed that the fusion zone (FZ) consisted predominantly of FCC and BCC phases, without the formation of detrimental intermetallic compounds. Coarse columnar and cellular grains evolved in the FZ due to high heat input. Largely, the developed DSS-HEA dissimilar weld provided a balanced synergy of strength and ductility, with strength contributed by the BCC phase and ductility provided by the FCC phase. The YS and UTS of the dissimilar joint were significantly improved than the similar HEA-HEA weld, with a 5 % improvement in the ductility compared to the similar HEA-HEA weld. Furthermore, the ductility of the dissimilar joint (DSS-HEA) was significantly increased when compared to the similar DSS-DSS weld. Fracture surface analysis indicated a transition from brittle to ductile fracture across the different welds, with the similar DSS-DSS weld exhibiting brittle fracture, characterized by cleavage planes and minimal plastic deformation, while the similar HEA-HEA and dissimilar HEA-DSS welds demonstrated more ductile features, with extensive dimple formation and improved strain accommodation. This study provides valuable insights into the mechanical performance of dissimilar welds and these findings pave the way for future research into optimizing dissimilar welds for industrial applications and advanced manufacturing sectors requiring high toughness and durability. • Successfully joined dissimilar CoCrFeMnNi-High Entropy Alloy (HEA) and Duplex Stainless Steel (DSS) using optimized laser beam welding parameters, achieving defect-free welds. •Demonstrated no intermetallic formation in the fusion zone, highlighting the effectiveness of the welding process. •Achieved significant improvements in mechanical properties: 11 % higher yield strength, 19 % higher ultimate tensile strength, and 5 % higher ductility compared to similar HEA welds. •Microstructural analysis revealed fine grain refinement, carbon depletion, and deformation twins contributing to enhanced weld strength and ductility.