Hydrogen-induced nanohardness variations in a CoCrFeMnNi high-entropy alloy

Abstract

The influence of electrochemically charged hydrogen (H) on the hardness (HN) of a CoCrFeMnNi high-entropy alloy (HEA) was investigated with nanoindentation. Upon charging, HN of HEA increases by ∼60%, which decreases gradually during subsequent aging at room temperature, and on prolonged aging, the alloy softens to an extent that HN falls below that of the uncharged HEA. These H-induced mechanical property variations are rationalized in terms of the competition between solid solution hardening caused by H and excess vacancy creation due to deeply trapped H.