The influence of silicon and phosphorus additions on neutron induced microstructural evolution of Fe-Cr-Ni ternary alloys at 646-703 K

The influence of silicon and phosphorus additions on void swelling in austenitic stainless steels under fast neutron irradiation has been investigated. A series of silicon containing alloys (Fe-15Cr-20Ni-Si) and two series of phosphorus containing alloys (Fe-15Cr-25Ni-P and Fe-16Cr-17Ni-P) were irradiated in the temperature range of 646-703 K and 2 to 36 dpa. Fast neutron irradiation was performed in both FFTF and JOYO. Non-monotonic swelling in response to the solute level was observed in alloys with higher nickel content and at the solute levels where precipitation was not prominent. The enhanced void swelling observed at relatively low solute levels was mirrored by an enhanced void density. The results suggest that the enhancement of swelling by solute addition occurs when void nucleation was initially difficult. (orig.)