Multiscale investigation of crack path and microstructural changes during liquid metal embrittlement of 304L austenitic steel in liquid sodium.
Résumé
Fracture micro-mechanisms and crack path of embrittled austenitic steel 304L by liquidsodium at 573K are investigated underneath the fracture surface by transmission electronmicroscopy down to the nanoscale. Automated crystal orientation and phase mappinganalyses show that abundant martensitic transformation (et947;et61664;et945;-) as well as mechanicaltwinning occur during the deformation of austenite and play a major role in the fractureprocess. A correlation between the fracture surface features and the underlyingmicrostructural interfaces is evidenced, strengthening the conclusion that liquid metalembrittlement by sodium of austenitic steels is basically an interfacial cracking phenomenon.