Multiscale investigation of quasi-brittle fracture characteristics in a 9Cr-lMo ferritic-martensitic steel embrittled by liquid lead-bismuth under low cycle fatigue

摘要

Liquid metal embrittlement (LME) induced quasi-brittle fracture characteristics of a 9Cr-lMo ferritic-martensitic steel (T91) after fatigue cracking in lead-bismuth eutectic (LBE) have been investigated at various length scales. The results show that the LME fracture morphology is primarily characterized by quasi-brittle translath flat regions partially covered by nanodimples, shallow secondary cracks propagating along the martensitic lath boundaries as well as tear ridges covered by micro dimples. These diverse LME fracture features likely indicate a LME mechanism involving multiple physical processes, such as weakening induced interatomic decohesion at the crack tip and plastic shearing induced nano/micro voiding in the plastic zone. (C) 2015 Elsevier Ltd. All rights reserved.