Effects of Nickel, Phosphorous and Sulfur on the Post-Irradiation Annealing Behavior of Irradiation Hardening in Fe–0.2 mass% C–0.3 mass% Cu Model Alloys

Abstract

Micro-Vickers hardness and positron lifetime were measured after 1 MeV proton irradiation to a fluence of 3 × 10¹⁷ ions/cm² at below 80°C and post-irradiation isochronal annealing to 650°C to investigate the effects of nickel (Ni), phosphorous (P) and sulfur (S) on the irradiation hardening of Fe–0.2 mass% C–0.3 mass% Cu model alloy. With increasing the Ni content to 0.6 mass%, irradiation hardening was increased, while a further increase to 1 mass% resulted in a small reduction. The addition of 0.05 mass% P increased the irradiation hardening of the model alloys irrespective of the addition of 0.6 mass% Ni, while the addition of 0.05 mass% S showed almost no effect on the hardening. Positron lifetime measurements revealed that the intensity of long-lifetime component, namely the number density of microvoids, increased and decreased for the alloy added with P and S, respectively. However, no significant effect of Ni content on the long-lifetime component was observed. Post-irradiation anneal-hardening was large and became a maximum at around 350–375°C in most of the alloys studied. The addition of 0.6 mass% Ni caused almost no effect on the annealing behavior, while further addition of 0.05 mass% P reduced the hardness change by the annealing to 400°C. During post-irradiation annealing to around 400°C, the long-lifetime component increased in the alloy with P, but it was so small in the alloy with S or manganese (Mn). These suggest that P enhances the growth of the microvoids but S as well as Mn suppress it.