Void Swelling and Precipitation in Ti-Modified Austenitic Fe-Ni-Cr Alloys

Abstract

Irradiation temperature dependence of void swelling, and the effects of aging before irradiation on void swelling and on precipitation were examined in three Ti-modified austenitic steels called No. 1 (Fe-14Ni-16Cr-1.8Mn-2.4Mo-0.1Nb-0.1Ti-0.9Si-0.07C), No. 2 (Fe-14Ni-15Cr-1.6Mn-2.6Mo-0.24Ti-1.0Si-0.06C) and No. 3 (Fe-25Ni-15Cr-1.6Mn-2.4Mo-0.4Ti-1.0Si-0.06C). After irradiation to 10 dpa with 150–200 keV proton, the cold worked No. 1 showed swelling peak of 0.4% at 823 K, the cold worked No. 2 0.15% at 773 K and the cold worked No. 3 0.08% at 723 K. Sample Nos. 2 and 3 which were aged at 923 K for 5.4 Ms (1,500 h) showed larger void swelling because of higher void number density than the unaged ones after the irradiation to 20–40 dpa at 923 K. The amount of intragranular TiC precipitates in the irradiated specimens did not vary significantly with preirradiation treatments. Voids were mostly attached to eta (M6C) phase which was produced during irradiation. The number density of eta phase produced during the irradiation in aged specimens was much higher than that in unaged ones. This is thought to give a main reason why void swelling in aged specimens was larger than that in unaged ones.