Improving the hydrogen embrittlement resistance of a selective laser melted high-entropy alloy via modifying the cellular structures

We demonstrate that modifying the cellular structures by well-controlled annealing can effectively improve the hydrogen embrittlement (HE) resistance of selective laser melting (SLM) processed alloys. Investigations on both as-SLM processed and annealed prototype CoCrFeMnNi high-entropy alloy samples suggest that annealing preserved the cellular structures while effectively reduced the dislocation densities. This slightly reduced the strength but significantly increased the ductility and HE resistance upon slow strain rate tensile tests (1 x 10(-5) s(-1)) under in situ electrochemical hydrogen charging. The crack initiation and propagation were delayed by hydrogen-enhanced local plasticity with the formation of nano-twins and dislocation cells in the modified structures.