Slow strain rate tensile tests on T91 in static lead–bismuth eutectic

The embrittlement effect of liquid lead–bismuth eutectic (LBE) on martensitic steel T91 has been studied by performing slow-strain-rate tensile (SSRT) tests in static LBE with about 1 wppm oxygen at temperatures ranging from 250 °C to 425 °C. Two groups of samples were used. Group-I samples with microcracks on the lateral surfaces indicated clearly LBE embrittlement effect at temperatures ⩾300 °C, while Group-II samples without microcracks did not show the effect. The LBE embrittlement effect occurred after the necking of specimens started. The yield and ultimate tensile strengths and uniform elongation were not affected. SEM observations showed the specimens ruptured in a brittle fracture mode when the embrittlement occurred. It is concluded that the requirements for the susceptibility of LBE embrittlement effect on the T91 steel are: surface cracks or flaws, wetting and a certain level of stress concentration at crack tips.