Microstructural Evolution and Mechanical Properties of Laser Beam Welded AlxCoCrFeNi High Entropy Alloys

AlxCoCrFeNi high entropy alloy (HEA) system has received extensive attention of researchers as it shows a dynamic change in phase fraction and properties in response to variation in the Al content. In this study, AlxCoCrFeNi HEAs were welded using a laser beam welding and microstructural evolution and mechanical properties were studied using X-ray diffraction, electron backscatter diffraction, scanning electron microscopy, hardness and tensile tests. Results revealed that, the laser-welded Al0.3 alloy exhibited an increased tensile strength but a minor decrease in ductility as compared to that of the base metal (BM) Conversely, the laser-welded Al0.5 and Al0.7 alloys, characterized by a dual-phase structure, demonstrated a simultaneous decrease in both strength and ductility. The hardness of Al0.3 increased from 156 HV for base metal (BM) to 197 HV for weld zone (WZ). A drastic drop in the hardness in the fusion zone was observed for Al0.5 (from 242 HV for BM to 212 HV for WZ) and Al0.7 (from 387 HV for BM to 260 HV for WZ). The decrease in hardness for welded Al0.5 and Al0.7 alloy may be attributed to reduced fraction of secondary BCC/B2 phase in the microstructure. Texture analysis of the welded samples reveals columnar grains with a $$<100>\parallel {\text{ND}}$$ texture fibre in the welded Al0.3 and Al0.5 alloys. However, the welded Al0.7 alloy has a dendritic structure with random texture due to the enhanced rate of constitutional supercooling arising from the higher fraction of secondary phases. The combined effect of changes in phase distribution, texture, and grain size might be the reasons for the variation in mechanical properties of the welded alloy.