The risk of liquid metal embrittlement of the Z10CDNbV 9-1 martensitic steel

The aim of this work was to determine the factors likely to lead to a liquid metal embrittlement of the Z10CDNbV9-1 martensitic steel. Monotonic tensile tests carried out from 533K to 623K in air showed a ductile behaviour and ductile fracture of the alloy even if the highest hardness had been obtained for a given tempering temperature and even if sharp defects existed on the specimen surface. In most cases, no effect of the liquid metal (lead, tin, lead-bismuth eutectic) was noticed compared with the tensile behaviour in air. A liquid metal emhrittlement was however observed in the 773K tempered steel when microcracks form at the surface of the specimen, exposing thus fresh surfaces to the liquid metal, before microvoids nucleate and grow in the specimen bulk. From the fractographic investigation clearly showing transgranular cleavage and from atomic scale simulation, it is proposed that a reduction of the surface energy caused by the adsorbed atoms of the liquid metal is responsible for the embrittlement