Crack path and liquid metal embrittlement specificity of austenitic steels in mercury at room temperature

A liquid metal embrittlement specificity of three austenitic steels with increasing nickel content (304 L, 316 L and 316L(N)) is studied in liquid mercury in the axisymmetric notched geometry. Only the low nickel alloys are susceptible to LME. The crack path of an austenitic steel fracture induced by liquid mercury has been elucidated at microstructural scale. Deformation induced martensite (gamma(fcc)-> alpha'(bcc)) of the low nickel steels induces numerous alpha'/alpha' interfaces at small scale that are susceptible to be embrittled. Because the only steel that resists LME is the one that shows stability over alpha' phase change due mostly to its higher nickel content, a point confirmed by X Ray fractography, it is inferred that the major factor contributing to the LME sensitivity at room temperature is the alpha' phase formation in unstable austenitic steels during plastic strain. This provides a sound rationale on how to prevent mercury induced embrittlement with austenitic steels.

Automated summary

This study investigates the liquid metal embrittlement behavior of three austenitic steels with increasing nickel content in liquid mercury. It is found that only the low nickel alloys are susceptible to embrittlement. The crack path of austenitic steel fracture induced by liquid mercury is elucidated at the microstructural scale, with deformation induced martensite formation and the presence of alpha'/alpha' interfaces identified as key factors contributing to embrittlement. The results highlight the importance of alpha' phase formation in unstable austenitic steels during plastic strain in determining the sensitivity to liquid metal embrittlement.