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 degrees 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 degrees. 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 gamma -> alpha martensite formation by the spreading of a Shockley partial dislocation over successive < 111 >(fcc) planes. (C) 2007 Published by Elsevier B.V.