Swelling and microstructure of pure Fe and Fe–Cr alloys after neutron irradiation to ∼26 dpa at 400 °C

The microstructures of pure Fe and various Fe–Cr binary alloys in both the annealed and heavily cold worked conditions were investigated after irradiation to 25.8 dpa at 4 × 10−7 dpa s−1 in the BR-10 fast reactor. Microscopy has shown that the largest swelling of 4.5% was observed in the cold worked pure iron while that of annealed Fe is only 1.7%. Additions of 2% chromium resulted in a decrease of swelling, but the swelling of cold worked Fe–2Cr alloy was still higher than that of the annealed condition. Independent of the initial starting condition, swelling in the Fe–6Cr alloy was completely suppressed. In alloys with higher chromium content swelling of 0.04–0.05% was observed only in samples irradiated in the annealed condition. There were also significant changes in dislocation and precipitate microstructure.