AN ANALYSIS OF RADIATION EFFECTS IN MODEL A533B PRESSURE VESSEL STEELS CONTAINING COPPER, PHOSPHORUS AND NICKEL ADDITIONS

摘要

An existing database of small angle neutron scattering (SANS) spectra on a series of model A533B alloys containing various copper, phosphorus or nickel additions, before and after 290°C neutron irradiation to 3.1×10~(23) n.m~(-2) (E>1 MeV), is re-analysed using a Maximum Entropy computing procedure. Volume fraction - particle size and number density data are produced for each alloy to characterize the irradiation-induced microstructural changes in terms of microvoids and/or precipitates of different sizes. The calculations are further refined by introducing a compositional dependence to the irradiation-induced precipitates, assumed to be of the type CuNiMn. The derived particle size distributions are characterized by narrow sharp peaks at ~2 run diameter and broader peaks in the range 10-40 nm diameter. The analysis suggests that under irradiation the total volume fraction of precipitates increases with phosphorus content, and that there is an increase in volume fraction with increase in both copper and nickel content at constant phosphorus level. Most of the volume fraction increase in low-P steels arises from 1-4 nm diameter precipitates, whilst for high-P steels there is evidence of a significant increase in 4-50 nm diameter precipitates. Estimates of radiation hardening based on input of the SANS data into hardening models are in accord with measured values.