Gradient-structured high-entropy alloy with improved combination of strength and hydrogen embrittlement resistance

High-strength materials usually exhibit poor hydrogen embrittlement resistance, and thus, there are demands for materials with high strength and good ductility under hydrogen. Here, gradient structures containing surface nanotwins are introduced in a CrMnFeCoNi high-entropy alloy by surface mechanical attrition treatment, and hydrogen embrittlement resistance is compared with coarse- and nano-structured alloys produced by high-temperature homogenization and high-pressure torsion, respectively. The coarse-grained alloy shows high ductility, but its yield stress is low. The nanostructured alloy shows ultrahigh yield stress, but with poor hydrogen embrittlement resistance. The gradient-structured alloys have both high yield stress (500–700 MPa) and good ductility (15–33%) under hydrogen.