Ultrahigh hardness with exceptional thermal stability of a nanocrystalline CoCrFeNiMn high-entropy alloy prepared by inert gas condensation

摘要

(CoCrFeNi)(93.5)Mn-6.5 nanocrystalline high-entropy alloy (nc-HEA) with an average grain size of 25 nm was prepared by inert gas condensation (IGC) using a laser evaporation source. An unprecedented increment in hardness was found from 484 HV to 791 HV after annealing at 600 degrees C for 1 h. More surprisingly, the original high hardness is maintained even after annealing at 1100 degrees C, which demonstrates superb thermal stability of the nc-HEA. The underlying strengthening mechanism is attributed to the unique microstructure of the nc-HEA and its evolution during annealing. This study provides a new preparation technique (laser-IGC) for high-performance nc-HEAs with great potential for applications. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.