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

When structural materials are exposed to liquid metals and stress is applied, they may undergo abrupt brittle failure known as liquid metal induced embrittlement. (LME). LME is characterized by a premature brittle failure of otherwise ductile materials when placed in contact with a given liquid metal, specific for the material under stress. Among the parameters influencing the severity and the occurrence of LME, temperature, strain rate, microstructure, hardness, solubility, etc., the first two namely temperature and strain rate are most important and will directly affect the severity of embrittlement of the given brittle liquid metal, solid metal couple. According to the existing understanding of the phenomena of LME, the latter is severest at temperatures close to the melting temperature of the embrittling metal. At higher temperatures, the phenomena of LME occur with the same severity or the severity decreases until it disappears, so forming a temperature interval within which the material is susceptible to LME. This is known as the ductility trough. The size of this interval is constant for a given strain rate and is reported to decrease with decreasing strain rate with possible absence at sufficiently low strain rate. In this work, the effect of the temperature on the susceptibility of LME on one of the most promising candidates for cladding and high temperature parts of ADS MYRRHA material T91 was investigated at fixed strain rate (5.10-5 s-1) with all other conditions kept constant. The tests have been performed in liquid metal tests station one (LIMETS 1) specially designed for carrying out tests under precisely controlled liquid metal condition, temperature and dissolved oxygen concentration. The effect of the liquid metal was estimated by comparison between the tests in liquid metal and in 5%H2+Ar atmosphere.