Deformation-induced martensite formation and dislocation channeling in neutron-irradiated 316 stainless steel

The deformed microstructure in 316 stainless steel (316SS) after neutron irradiation in the range of 65–100 °C to 0.78 dpa was investigated by transmission electron microscopy (TEM). Deformation-induced martensite transformation and dislocation channeling were observed at irradiation dose higher than 0.1 dpa. Estimation of the resolved shear stress (RSS) associated with each dislocation channel indicated a tendency for the RSS and channel width to be greatest when the angle between tensile axis and slip plane normal is around 45°. Furthermore, channel width increased with increasing RSS, indicating that the most extensive localized channel deformation tends to occur at a high RSS level. Deformation-induced martensite phase was found at various strain levels even at room temperature and tends to be exhibited mainly at intersections of channels. This suggests that a very high stress could lead to the γ → α martensite formation by the spreading of a Shockley partial dislocation over successive 〈1 1 1〉fcc planes.