MICROSTRUCTURE OF FE-16NI-15CR ALLOYS IRRADIATED IN JOYO

Fast neutron irradiation were conducted on a set of model alloys with compositions of Fe-16Ni-15Cr-X (X=Ti, Nb and/or C) to study the effects of Ti, Nb and/or C additions on microstructural evolution during irradiation. The irradiations were carried out by using a fast breeder experimental reactor JOYO at 673 K to 0.8 and 8.1×1024 n/m2 (E>0.1 mev) and followed by TEM observations. Void swelling for these alloys was estimated to be very low, indicating that it remains in a transient region. C and Ti were found to suppress void nucleation effectively. Nb and C, on the other hand, enhanced nucleation for voids with an increase in void sizes. Pre-existing dislocations were concluded to provide preferential sites for void nucleation regardless of Ti, Nb and/or C additions. The irradiations produced faulted loops of interstitial-type on (111) planes. The morphology of these faulted loops was characteristically altered by the additions of C, Ti and/ or Nb.