An internal friction working model to advance the understanding of effects of radiation and thermal ageing on reactor pressure-vessel steels

Abstract

Temperature- and amplitude-dependent internal-friction measurements have been carried out on JRQ A533B Cl.1 steel, in order to investigate the influence of neutron irradiation and thermal ageing on this material. Neutron irradiation decreases the internal friction maximum observed in the vicinity of 315 K; this decrease is attributed to a reduction in the dislocation mobility by copper-rich clustering. Thermal ageing (3 years, 300 °C) clearly influences the internal friction highlighting the sensitivity of the technique. A new working model—referred to as the new interpretation, based on a linear combination of seven dislocation-related relaxations—is introduced to provide a basis from which to explain more in detail the qualitative effects of thermal ageing and irradiation. Amplitude-dependent results provide a measure of the yield stress which is compared with static tensile data and with a model for the yield stress comprising long- and short-range interactions. Neutron irradiation results in an athermal increase in the yield stress, while thermal ageing influences only the thermally activated part of the yield stress. The model is refined to explain the effects of thermal ageing and irradiation.