Tailoring hydrogen embrittlement resistance of pure Ni by grain boundary engineering

By using thermo-mechanical processing, 99.996 wt.% pure Ni with different grain boundary characteristics were fabricated (Sample #1, 700 degrees C x 10 h + cold rolling reduction 50% + 650 degrees C x 2 h; Sample #2, 700 degrees C x 10 h + cold rolling reduction 50% + 900 degrees C x 5 min). Hydrogen embrittlement sensitivity of the two samples was determined by using high-pressure hydrogen charging, low strain rate tensile test and SEM fractography. Compared with Sample #1, hydrogen embrittlement index of Sample #2 increased from 0.52 to 0.71. The effects of grain size, grain boundary type and grain boundary curviness on hydrogen embrittlement of pure Ni were discussed. The results indicate that: 1) special grain boundaries including twin grain boundaries may have a marginal effect on tailoring hydrogen embrittlement resistance in pure Ni; 2) increasing grain boundary curviness is an effective way to improve hydrogen embrittlement resistance of Ni. (c) 2022 The Author(s). Published by Elsevier B.V. on behalf of Institute of Metal Research, Chinese Academy of Sciences. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )