Austenitic stainless steels are used for the internals components of Light Water Reactors (LWRs). Neutron irradiation affects their nanostructure, leading to evolutions of deformation mechanisms - increase of grain scale slip localization - and mechanical properties - increase of yield stress and decrease of strain hardening capability. Irradiation also increases their susceptibility to Intergranular Stress Corrosion Cracking (IGSCC). A correlation is reported between IGSCC initiation and slip band localization: the stronger the localization, the higher the susceptibility to IGSCC, with cracking at Grain Boundaries (GBs) correlated with slip discontinuity. Therefore, slip band localization and continuity at grain boundaries are both assessed in this study to provide quantitative data relevant for IGSCC modelling. In-situ Scanning Elect1ron Microscope (SEM) tensile tests were performed at 320 ∘ C on un-irradiated and 1 dpa proton-irradiated 304 stainless steels. Large area SEM maps allow evaluating statistically the number of intragranular slip bands and slip continuity / discontinuity at GBs for three levels of applied strain (2.5%, 5% and 10%). Slip band analysis allows determining the slip normals and directions, either using Schmid assumption or directly based on particle tracking at the samples surfaces. A model proposed in the literature predicting the increase of slip band number as a function of strain and grain size is shown to yield quantitative predictions once calibrated. Slip discontinuity at general grain boundaries is found to be well described by a criterion involving the Luster - Morris (LM) parameter m ′ ≤ 0.7, insensitive to irradiation and strain levels within the ranges considered, and similar to the one put forward for other Face Centered Cubic (FCC) materials. Slip (dis)-continuity at Σ 3 grain boundaries and implications of the results for IGSCC mitigation strategies and modelling are finally discussed.
Masset et al. (Fri,) studied this question.