Understanding the limits of lattice orientation data analysis in environmental degradation studies

Cold working can significantly increase the susceptibility of metals to environmentally assisted cracking. However, the reasons for this increase susceptibility are still unclear. This is due in part to the difficulty in quantifying and modelling plastic deformation at the required scale. Here, we use a new experimental procedure to study the local microstructural distribution of strain in 304L stainless steel. Digital image correlation was used to map strain at the microstructural level with sub-micron resolution. The results clearly show that a high degree of strain localization develops within individual grains, in the form of highly localized shear bands and micro-twinning. Electron backscatter diffraction was used to quantify the lattice orientation changes in the same area. Analysis of this data included the calculation of kernel average misorientation and of intragranular orientation spread following grain reconstruction. Comparisons of results clearly show that, in most cases, there is no evidence in the lattice orientation data analysis of the high levels of strain measured. This has important implications in the use of lattice orientation data in the study of the effects of plastic deformation on environment-assisted cracking.