Strong resistance to hydrogen embrittlement of high-entropy alloy

The resistance to hydrogen embrittlement (HE) of CrMnFeCoNi high-entropy alloy (HEA) at both room and cryogenic temperatures was examined through tensile experiments on specimens hydrogenated via cathodic electrochemical charging method. Two representative steels, i.e. 316L stainless steel (SS) and X80 pipeline steel (PS), were chosen for comparison due to their similar main constituent elements to CrMnFeCoNi HEA. Results show that the hydrogen pre-charged CrMnFeCoNi HEA has the smallest loss of ductility among the three materials at room temperature, while displays no reduction of elongation at 77 K, compared with the uncharged one. Fracture surfaces at both room and cryogenic temperatures of hydrogen pre-charged CrMnFeCoNi HEA are mainly composed of dimples, indicating ductile fractures, while brittle characteristics occur in pre-charged 316L SS and X80 PS. Typical deformation microstructure of the hydrogen pre-charged CrMnFeCoNi HEA at room temperature is tangled dislocations instead of highly dense dislocation walls (HDDWs) found in the pre-charged 316L SS. At 77 K, more deformation twins are formed in the both materials. Reasons for a higher resistance to HE of CrMnFeCoNi HEA at room temperature are attributed to the formation of less hydrogen trapping sites, thus a lower degree of hydrogen enrichment than 316L SS. While at 77 K, the atomic hydrogen is not able to promptly accumulate near these trapping sites due to its slow diffusion rate, which leads to strong HE resistance.