Dose dependence of void swelling and precipitation behavior in MC carbide dispersed austenitic Fe-Ni-Cr alloys

The correlation between void swelling and phase stability of MC precipitates under proton irradiation was examined. Four 10%-cold-worked Fe-25Ni-15Cr-0.07 C alloys, which contain either 0.24 Ti, 0.41 Zr, 0.23 Ti + 0.97 Si, or 0.19 Ti + 0.10 Nb in wt%, respectively, were irradiated at 823 K by 200 keV protons to the doses of 10, 20, 30 and 40 dpa. The alloy containing 0.41 Zr showed the largest swelling and had very few ZrC precipitates. The alloy containing 0.23 Ti + 0.97 Si showed extremely low swelling. In the alloys which contain 0.24 Ti and 0.19 Ti + 0.10 Nb, respectively, the number density of the fine MC precipitates produced at the initial stage of irradiation decreased significantly with increase in dose from 10 to 40 dpa, and coarse, rod-shaped MC precipitates appeared at 20 dpa and grew with increasing dose. The rapid increase of the swelling rate with increase in dose from 10 to 40 dpa observed in these alloys was thought to be caused by the decrease of the sink strength of the MC precipitates. (orig.)