An experimental study of the polycrystalline plasticity of austenitic stainless steel

Abstract

The development and validation of crystal plasticity models requires the ability to map deformation at the microstructural scale. Here, a new method of high-resolution deformation mapping is used to measure strain, material rotation and lattice rotation in austenitic stainless steel at sub-micron resolution. Electron back-scatter diffraction maps are used to link the deformation to the microstructure. Deformation occurs in domains, in which most of the plastic strain originates from the activation of a single slip system with high resolved shear stress. Within domains, slip is localized in lamellar regions that increase in number with strain. The deformation incompatibility between grains that develops as a consequence of this single crystal like behaviour is accommodated by either a gradient in slip intensity and the consequent development of lattice curvature at the grain boundary or the activation of an additional high stressed slip system and the consequent formation of a complementary deformation domain within the grain. In many cases, however, lattice curvature across grain boundaries is small because the deformation domains in neighbouring grains are compatible. The implications of these observations for continuum crystal plasticity modelling are discussed.