Multiscale investigation of crack path and microstructural changes during liquid metal embrittlement of 304L austenitic steel in liquid sodium

Abstract Fracture micro-mechanisms and crack path of embrittled austeniticsteel 304L by liquid sodium strained at 4.2 × 10 −7 m s −1 and 573 K are investigated underneath the fracture surface by transmission electron microscopy down to the nanoscale. Automated crystal orientation and phase mapping analyses show that abundant martensitic transformation (γ austenite→ α’ martensite) as well as mechanical twinning occur during the deformation of austeniteand play a major role in the fracture process. A correlation between the fracture surface features and the underlying microstructural interfaces is evidenced, strengthening the conclusion that liquid metal embrittlementby sodium of austeniticsteels is basically an interfacial cracking phenomenon.