Crack path in liquid metal embrittlement: experiments with steels and modeling

Abstract

We review the recent experimental clarification of the fracture path in Liquid Metal Embrittlement with austenitic and martensitic steels. Using state of the art characterization tools (Focused Ion Beam and Transmission Electron Microscopy) a clear understanding of crack path is emerging for these systems where a classical fractographic analysis fails to provide useful information. The main finding is that most of the cracking process takes place at grain boundaries, lath or mechanical twin boundaries while cleavage or plastic flow localization is rarely the observed fracture mode. Based on these experimental insights, we sketch an ongoing modeling strategy for LME crack initiation and propagation at mesoscopic scale. At the microstructural scale, crystal plasticity constitutive equations are used to model the plastic deformation in metals and alloys. The microstructure used is either extracted from experimental measurements by 3D-EBSD (Electron Back Scattering Diffraction) or simulated starting from a Voronoï approach. The presence of a crack

Stability of fatigue cracks at 350 °C in air and in liquid metal in T91 martensitic steel

“…Moreover, it has been shown that oxygen in the liquid LBE can drive the Pb atoms to enter the lattice along the channels formed in the cracked oxide [24]. Brittle fracture initiates and propagates along all types of interfaces such as lath interfaces, block interfaces, packet interfaces and martensitic grain boundaries in agreement with the findings of Auger et al [25]. Brittle fracture propagation through lath or packet is not excluded but due to the size of these microstructural items, it is difficult to decide.…”

A graph based workflow for extracting grain-scale toughness from meso-scale experiments

“…( 8) to the ground truth values produced by the Eq. (7). To this end the two functions are plotted and the surface plots are presented in Fig.…”

“…Interface controlled fracture is an important phenomenon present in many structural alloys such as Al-Li [1,2], β-Titanium alloys [3], multi-phase steels [4] and ceramics [5][6][7]. Similarly, when exposed to aggressive chemical agents (e.g.…”