Immunity of Al0.25CoCrFeNi high-entropy alloy to hydrogen embrittlement

The influence of hydrogen via electrochemical charging on the mechanical behavior of the cryo-rolled and annealed Al0·25CoCrFeNi high entropy alloy (HEA) through tensile experiments was investigated. The results indicated that the Al0·25CoCrFeNi alloy mainly composed of FCC phase has immunity to electrochemical hydrogen embrittlement. Analysis on the fracture surfaces revealed that hydrogen permeates into a shallow depth and transforms the deformation mechanism. The deformation twins and stress-induced phase transformation (FCC-to-HCP) are introduced in the surface near fracture of tensile sample when the Al0·25CoCrFeNi alloy is not charged by hydrogen. After hydrogen charging, the dissolved hydrogen decreases the stacking fault energy and promotes the planar dislocation slip, resulting in the enhancement of strength and ductility in Al0·25CoCrFeNi HEA.