In-situ neutron diffraction study on hydrogen embrittlement of 316L at cryogenic temperatures

There is a great need for further research to be carried out on hydrogen embrittlement at lower temperatures. At low temperatures the volumetric energy density can be significantly increased and one key drawback in the use of hydrogen as a net zero fuel source can be combatted. This becomes more complex when studying 316L steel which already deforms in different modes as the temperature decreases from room temperature. Many studies have declared that hydrogen will reduce the stacking fault energy (SFE) of 316L from observations of early onset of twinning, but a recent study challenged this using in situ neutron diffraction at room temperature and deduced that the early onset of twinning is due to a change in solid solution strengthening. I propose that in situ neutron diffraction tests during cryogenic deformation to be carried out on hydrogen charged specimens, analysing the changes in deformation as the temperature is reduced, when twinning deformation and strain induced martensite transformation becomes more prevalent due to the temperature-dependent SFE being reduced. By studying the hydrogen affects in the lower temperature range down to liquid hydrogen temperature, additional findings on how hydrogen embrittlement will affect 316L storage tanks when storing cryo-compressed or liquid hydrogen can also be made.

针对低温环境下的氢脆现象，仍有大量研究工作亟待开展。在低温条件下，氢能的体积能量密度可得到显著提升，同时也能解决氢能作为净零排放燃料源所存在的一项关键弊端。而当研究316L钢时，情况会更为复杂：随着温度从室温逐步降低，该钢材的变形模式已会发生改变。此前诸多研究通过观察到孪生变形的提早萌生现象，提出氢能会降低316L钢的层错能（Stacking Fault Energy, SFE），但近期一项研究在室温下利用原位中子衍射（in situ neutron diffraction）对该结论提出了质疑，并推断孪生变形的提早萌生实则源于固溶强化效应的变化。笔者提出，应对充氢试样开展低温变形过程中的原位中子衍射测试，分析温度降低过程中的变形变化——此时由于温度依赖性层错能的降低，孪生变形与应变诱导马氏体相变将愈发普遍。通过在低至液氢温度的低温区间内研究氢的影响，还可进一步探明氢脆在储存低温压缩氢或液氢时，会对316L钢储氢罐产生何种作用。