NEUTRON-IRRADIATION AND INTERGRANULAR FRACTURE IN VANADIUM-20 WT-PERCENT TITANIUM-ALLOYS UNDOPED AND DOPED WITH PHOSPHORUS AND SULFUR

The mechanical properties and grain boundary composition affected by n eutron irradiation (9.8 x 10(24) n/m(2): E > 0.1 MeV at 438 degrees C) in undoped, P-doped and S-doped V-20 wt% Ti alloys all containing res idual C and O have been studied using a small punch testing method and scanning Auger microprobe analysis. Neutron irradiation facilitated h eterogeneous formation of intergranular microcracks, not leading to sp ecimen failure, in all undoped and some S-doped specimens. An irradiat ed undoped alloy indicated ductility loss to a smaller extent than exp ected from the easy microcracking due to a mixture of intergranular an d transgranular macrocracking. The irradiation effect on the ductility varied in the S-doped alloy, while the irradiation exerted a benefici al effect on low temperature ductility in P-doped alloys. Intergranula r S segregation in the undoped alloy and S desegregation in the S-dope d alloy occurred during the ii-radiation. Unirradiated and irradiated P-doped alloys exhibited negligible S segregation and much smaller P s egregation than the S segregation in the undoped and S-doped alloys. T he grain boundary content of C affecting the ductility was remarkably reduced in the irradiated P-doped alloy and S-doped specimens with duc tility loss. The ductility loss and improvement observed in the irradi ated alloys are interpreted in light of the variations in segregated a nd precipitated impurities together with hardening behavior. (C) 1998 Elsevier Science B.V.