Effect of post weld heat treatment on the microstructure and mechanical properties of gas tungsten arc welded Al0.3CoCrFeNi high entropy alloy

In this work, a single-phase Al0.3CoCrFeNi high entropy alloy is successfully joined by gas tungsten arc welding (GTAW). Microstructural analysis revealed the presence of equiaxed grains and annealing twins in the base material, while the same FCC structure with coarse grains and columnar dendrites are identified in the heat-affected zone and fusion zones, respectively. Further, post-weld heat treatment (PWHT) of the welded joint at 1100 °C for 1hr facilitates the formation of B2/BCC precipitates in the FCC matrix. The as-received material showed an ultimate tensile strength of 570 MPa and elongation of 83 %. The joint efficiency is 82 %, which is attributed to the large grain size that developed in the fusion zone. The PWHT material had an improved joint efficiency of 92 %, attributed to BCC/B2 precipitates forming within the FCC matrix. This research highlights the role of PWHT in obtaining high-performing HEA joints.