RADIATION-INDUCED SEGREGATION IN FE-20CR-25NI-NB BASED AUSTENITIC STAINLESS-STEELS

A series of model alloys, based on the commercial 20Cr-25Ni-Nb stainless steel, have been irradiated in an HVEM using 1 MeV electrons, at temperatures between 250 and 500-degrees-C, to doses ranging from 0.6 to 7.2 dpa. The temperature and dose dependence of the segregation in the commercial alloy have been investigated and found to be strongly influenced by grain boundary migration. Cold work has been found to be useful in reducing segregation at low doses but loses any beneficial effects at higher doses as a result of extensive grain boundary migration. Enhanced segregation has been observed in the pure ternary and has been associated with a reduced number of recombination sites in the matrix. The relative insensitivity of the solute segregation to minor solute additions has been attributed to lack of defect trapping, which is due to the high dose rates employed in the HVEM.