Enhancing hydrogen embrittlement resistance in a non-equiatomic Fe0.5CoCrNi high-entropy alloy via Mo alloying: A Combined First-Principles and Experimental Study

This study employs first-principles calculations combined with experiments to investigate the effect of Mo alloying on the hydrogen embrittlement resistance of the non-equiatomic Fe 0.5 CoCrNi high-entropy alloy. The results indicate that Mo addition improves the hydrogen embrittlement resistance of the alloy. First-principles calculations show that Mo suppresses H2 dissociation and weakens atomic H adsorption on the alloy surface, as reflected by the increased H 2 dissociation energy and the raised H adsorption energy, an effect arising from the Mo-induced modification of the surface electronic structure combined with the local chemical environment. Surface work function and density-of-states analyses further indicate that Mo doping promotes electron delocalization and raises the work function, thereby improving the surface electrochemical stability. In addition, Mo converts the hydrogen dissolution energy at grain boundaries from a negative value (-0.135 eV) to a positive value (+0.089 eV), suppressing hydrogen dissolution at grain boundaries. Experimental results confirm that Mo enables the alloy to maintain excellent mechanical properties in hydrogen environments, exhibiting a mixed fracture mode combining ductile and brittle fracture characteristics. The experiments also verify that Mo effectively mitigates the weakening effect of H on grain boundary cohesive strength. This study elucidates the hydrogen embrittlement resistance mechanism of Mo at the atomic scale, providing a theoretical basis for the rational design of high-entropy alloys with superior hydrogen embrittlement resistance.