Modeling of irradiation hardening of iron after low-dose and low-temperature neutron irradiation

Irradiation hardening is a prominent low-temperature degradation phenomena in materials, and is characterized both by an irradiation-induced increase in yield strength along with the loss of ductility. In this paper, a reaction-diffusion cluster dynamics model is used to predict the distribution of vacancy and interstitial clusters in iron following low-temperature (<373 K) and low-dose (<0.1 dpa) neutron irradiation. The predicted microstructure evolutions of high-purity iron samples are compared to published experimental data (positron annihilation spectroscopy and transmission electron microscopy) and show good agreement for neutron irradiation in this regime. The defect cluster distributions are then coupled to a dispersed barrier hardening model that assumes a strength factor, a, which varies with cluster type and size to compute the yield strength increase; the results of which agree reasonably well with tensile tests performed in previous studies. The modeling results presented here compare quite well to the experimental observations in the low-dose regime, and provide insight into the underlying microstructure-property relationships and the need for spatially dependent modeling to accurately predict the saturation behavior of yield strength changes observed experimentally at higher dose levels.