Hydrogen‐assisted fatigue crack propagation behavior of equiatomic Co–Cr–Fe–Mn–Ni high‐entropy alloy

The equiatomic Co–Cr–Fe–Mn–Ni high‐entropy alloy (HEA) shows well hydrogen embrittlement resistance under monotonic tensile load. However, the fracture behavior under cyclic load is still unclear. In this study, combining with the fracture features analysis by electron back‐scattered diffraction and electron channeling contrast imaging techniques, the hydrogen‐assisted fatigue crack propagation behavior of equiatomic Co–Cr–Fe–Mn–Ni HEA under in situ electrochemical hydrogen charging was investigated. The results suggest that the hydrogen had significant accelerating effects on the fatigue crack growth rate of Co–Cr–Fe–Mn–Ni HEA. Intergranular cracking with the formation of dislocation cells was observed at low stress intensity range (ΔK) area, while transgranular cracking with deformation twins was observed at a high ΔK area. The formation of these deformation features was assisted by hydrogen‐assisted dislocation emission. Hydrogen‐assisted fatigue crack propagation behavior of Co–Cr–Fe–Mn–Ni HEA was investigated. Hydrogen significantly accelerates the fatigue crack growth rate. Intergranular cracking and dislocation cells were observed at low ΔK area. Transgranular cracking and deformation twins were observed at a high ΔK area. Hydrogen‐assisted dislocation emission assisted the formation of these deformation features.