Liquid metal embrittlement susceptibility of a high-entropy alloy exposed to oxygen-depleted liquid lead-bismuth eutectic at 250 and 350 °C

Liquid metal embrittlement (LME) susceptibility of a high-entropy alloy (HEA) with a nominal composition of Fe₄₀Mn₁₀Ni₁₀Co₂₀Cr₂₀ (at.%) and a single face-centered cubic (fcc) structure was tested in oxygen-depleted lead-bismuth eutectic (LBE, Pb_44.5Bi_55.5, wt%) and argon (Ar) environments at 250 and 350 °C using slow strain rate tensile tests. A nominal strain rate of 5x10^-5s^-1 was employed for all tests. The results showed that LBE had no evident impact on the tensile mechanical properties including total elongation to rupture. Fractographic examinations revealed that the fracture surfaces were predominately dimpled, regardless of the environment and temperature tested. All the results indicate that this high-entropy alloy is not susceptible to LME under the experimental conditions tested in this study. However, severe dissolution corrosion with a corrosion depth of 50-100 μm occurred at the surface, although the specimens were pre-exposed to the oxygen-depleted LBE at 450 °C only for about 20h. This was due to the high contents of Ni and Mn, which are two elements having a high solubility in LBE at a high temperature. The dissolution corrosion and the subsequent tensile loading resulted in formation of numerous microcracks at the specimen surface, contrary to the cases tested in Ar. In this regard, the high-entropy alloy is poorly resistant to LBE dissolution corrosion at 450 °C.