Gas tungsten arc welding of a multiphase CoCuFeMnNi high-entropy alloy

Since their inception, high-entropy alloys (HEAs) have been the subject of an increasing amount of research involving a plethora of compositions and environmental conditions. In line with this, research on their processability is crucial to achieve competitive alternatives to common engineering alloys for potential structural and functional applications. For such endeavors, gas tungsten arc welding (GTAW), which is widely used in industry to obtain monolithic parts from separate components, is capable of supplying pertinent information regarding the feasibility of combining new materials in terms of their microstructure and mechanical performance.

With this in mind, in the present work, we present an analysis of the feasibility of GTAW of CoCuFeMnNi HEA. This is accomplished by delving into microstructural observations using conventional and advanced techniques, such as synchrotron X-ray diffraction coupled with CalPhaD-based calculations, to fully comprehend the microstructure across the weld. The mechanical performance of the joints is also researched in terms of microhardness and tensile testing.

Overall, the dual-phase nature of the HEA is observed throughout the welded joint, where the nucleation of a B2 BCC phase is highlighted in the heat-affected zone. The obtained joints however, exhibit poor mechanical performance, which is attributed to the residual stresses and sizeable grains which develop within the solidifying molten pool.