GRAIN-BOUNDARY SEGREGATION OF IMPURITIES IN NEUTRON-IRRADIATED AND THERMALLY AGED VANADIUM ALLOYS

A comparison of intergranular impurity segregation induced during neut ron irradiation (9.8 x 10(24) n/m(2): E > 0.1 MeV at 438 degrees C for 2120 h) and thermal ageing has been made in V-20 wt% Ti alloys undope d, P-doped and S-doped all containing residual C and O. Intergranular S segregation in an undoped alloy and S desegregation in a S-doped all oy occurred during neutron irradiation. Thermal ageing produced a larg e increase in the S segregation in the undoped and S-doped alloys. How ever, unirradiated, thermally aged and irradiated P-doped alloys showe d little S segregation. The P-doped alloy had much smaller P segregati on than the S segregation in the undoped and S-doped alloys. The grain boundary enrichment of C, O and Ti was reduced during the irradiation but promoted by the thermal ageing. The defect/impurity interaction a ffecting the impurity solubility and fluxes is considered to control t he intergranular impurity segregation during the irradiation. (C) 1998 Elsevier Science B.V, All rights reserved.