Effects of temperature and strain rate on the mechanical properties of T91 material tested in liquid lead bismuth eutectic

The effects of temperature and strain rate on the susceptibility of one of the most promising candidate materials for cladding and high temperature components for ADS, Ferritic/Martensitic steel (T91), to liquid metal embrittlement have been investigated in the temperature interval 150-450 deg. C, at strain rates between 1 x 10-3 s-1 and 1 x 10-6 s-1. The effect of the liquid lead bismuth eutectic has been evaluated by comparison between tests in the liquid metal and in Ar with 5% H2. Although the untreated T91 material did not undergo liquid metal embrittlement and there was no apparent change in trends of the tensile properties as function of temperature or strain rate due to the liquid metal, the pre-exposed T91, which was exposed to oxygen poor LBE at 450 deg. C for 4000 h and tested at 450 deg. C did show a decrease in total elongation. The total elongation of the untreated T91 specimens in liquid lead bismuth and in H2/Ar-gas mixture followed the same dependence on the temperature up to 245 deg. C. At temperatures above 375 deg. C no results are available from testing in controlled gas environment however reference data measured on the same batch of steel in air are used for comparison. Varying the strain rate did not cause any deterioration in the tensile properties of the material in liquid metal compared to those in gas atmosphere. The results are discussed in terms of self-healing mechanism and crack initiation processes