Initial weldability study on Al0.5CrCoCu0.1FeNi high-entropy alloy

The weld solidification behavior, segregation tendency, phase formation, and cracking susceptibility of Al0.5CoCrCu0.1FeNi high-entropy alloy (HEA) were investigated. The AlCoCrCuFeNi alloy system has received wide attention due to its high temperature stability and strength retention. Characterization of the as-melted, heat-treated, and hot-rolled and heat-treated alloy conditions was performed and compared to thermodynamic CALPHAD-based calculations. Autogenous gas tungsten arc (GTA) and laser beam welding was done on the different alloy conditions. Microstructural changes in the fusion zone and heat-affected zone (HAZ) were investigated by optical microscopy and micro-hardness. Hot cracking susceptibility was evaluated using the cast pin tear test (CPTT). The fusion zone solidification microstructure of Al0.5CoCrCu0.1FeNi alloy consists of primary face centered cubic dendrites and interdendritic body centered cubic phase that forms at the end of solidification. GTA welding results in the partial dissolution of the interdendritic phase in the high-temperature HAZ, adjacent to the fusion boundary. Welding on the heat-treated alloy leads to HAZ softening due to the dissolution of strengthening nano-sized precipitates. No solidification cracking or HAZ liquation cracking was observed. Laser welding did not result in a drop in hardness or significant microstructural changes in the HAZ. The CPTT results correspond well with the predicted solidification temperature range (141 K) for Al0.5CoCrCu0.1FeNi alloy and its overall good weldability that was observed in the present work.