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Liquid metal embrittlement (LME) of steels is of renewed interest in the
framework of nuclear reactors and spallation neutron sources projects using liquid
metals as coolant. The structural materials for these systems are selected
according to their resistance to liquid metal corrosion, irradiation embrittlement
and compatibility with the coolant. These stringent constraints leave two classes
of materials, austenitic steels and martensitic/ferritic steels. The reference
materials for these systems are the 316L austenitic steel and the T91 martensitic
steel, a modified 9Cr1Mo alloy. LME of these materials in contact with mercury
(Hg) and (PbBi) has been demonstrated in various works [1,2]. The fracture mode
proceeds either by cleavage or by shear cracking depending upon the geometry
and the mechanical solicitation (mode I or mixed mode II/III). A fracture
mechanics approach (J-δa) has been developed in plane stress with thin sheets
allowing to a good approximation a measurement of the crack length by optical
means. Indeed one of the difficulties of fracture mechanics with a liquid metal
environnement is the fact that the medium is opaque and conductive. This
adaptation of fracture mechanics reduces the propagation problem to a quasi-2D
problem. It showed that the liquid metal reduces the energy required for crack
extension by 30 to 50% supporting the case for LME [3]. The mechanism of LME
in general is still a matter of debate and it is the purpose of this paper to report a
study of cracking induced by a liquid metal by Electron Back Scattering
Diffraction (EBSD).