Effect of hydrogen charging time on hydrogen embrittlement of CoCrFeMnNi high-entropy alloy

The effect of hydrogen on mechanical properties and failure mechanism of a CoCrFeMnNi high-entropy alloy was evaluated by in/ex-situ tensile tests and electron backscatter diffraction. The results indicate that yield strength first decreases and then increases as hydrogen charging time increases, which is attributed to the competition between the hydrogen-induced softening effect and the hydrogen-enhanced twinning formation effect. The hydrogen-uncharged sample shows the micro-void coalescence failure mechanism, whereas hydrogen-assisted cracking of the alloy initiates from grain boundaries and slip bands caused by plasticity-mediated decohesion mechanism. Crystallographic analysis demonstrates that {110}//ND grains and {001}//ND-{111}//ND grain boundaries are vulnerable to hydrogen embrittlement.