Deformation microstructure of proton-irradiated stainless steels

The deformation microstructure of proton-irradiated stainless steels may play a key role in explaining their irradiation-assisted stress corrosion cracking (IASCC) susceptibility. In the present study, three model alloys (UHP-304, 304 + Si, 304 + Cr + Ni) with different stacking fault energies (SFEs) were irradiated with 3.2 MeV protons at 360 °C to 1.0 and 5.5 dpa and then strained in 288 °C Ar atmosphere. The deformation microstructure of the strained samples was investigated using scanning electron microscopy and transmission electron microscopy. The results showed that the slip lines interacted with grain boundaries by grain-to-grain transmission, grain boundary sliding or deformation ledge formation at grain boundaries. Expanded channels, which were formed at locations where dislocation channels intersected the grain boundaries or other channels, were found predominately in the low SFE alloys UHP-304 and 304 + Si. The steps and shear strain at grain boundaries caused by channel expansion may increase the IASCC susceptibility in low SFE stainless steels by producing strain concentrations and inducing cracks in the oxide film.