Enhanced resistance to hydrogen embrittlement in a CrCoNi-based medium-entropy alloy via grain-boundary decoration of boron

作者：Chen, X. H.; Zhuang, X. Q.; Mo, J. W.; He, J. Y.; Yang, T.; Zhou, X. Y.^*; Liu, W. H.^*

来源：Materials Research Letters, 2022, 10(4): 278-286.

DOI：10.1080/21663831.2022.2033865

• Medium entropy alloy
• hydrogen embrittlement
• grain boundary segregation

We found boron doping can substantially reduce the ductility-loss in the CrCoNi medium-entropy alloy after gas-hydrogen charging, from similar to 71% to similar to 46%, while the fracture mode transfers from predominantly intergranular to ductile transgranular dominated. The two alloys have no difference in phase-structures (single face-center-cubic), grain sizes, and grain-boundary (GB) characters. However, atom probe tomography identified apparent GB decoration of boron up to 1.5 at.% and nanometer-scaled scattered borides in boron-doped CrCoNi. Such local chemical difference leads to enhanced GB cohesion and reduced hydrogen diffusivity along GBs, resulting in improved immunity against hydrogen-embrittlement and suppressed mechanical degradation in the boron-doped CrCoNi alloy. @@@ IMPACT STATEMENT We found grain-boundary decoration of boron can substantially enhanced resistance to hydrogen embrittlement in a CrCoNi-based medium-entropy alloy when exposing to high-pressure gas-hydrogen charging.