Mechanical behavior and microstructural evolution of vanadium alloys irradiated in ATR-A1

Abstract An irradiation experiment has been done in the ATR-A1 to investigate irradiation behavior of vanadium alloys in the low temperature regime from 200°C to 300°C with damage levels of 3 to 4 dpa. In creep measurements, creep tubes of V–3Fe–4Ti–0.1Si with inner pressures up to 165 MPa did not rupture during irradiation. The effective strain rate of creep was below 0.2% dpa−1 and it showed the same tendency as V–4Cr–4Ti alloys. In Charpy impact tests, all specimens of V–4Cr–4Ti–0.1Si and V–3Fe–4Ti–0.1Si showed brittle behavior at room temperature and the DBTT increased to 60–150°C. The fracture surface showed cleavage. Tensile tests conducted both at room temperature and at the irradiation temperature showed significant irradiation hardening and brittle responses. TEM showed that high densities of tiny defect clusters were formed in V–Cr–Ti and V–Fe–Ti alloys. Precipitates could not be seen in specimens irradiated below 300°C, however, fine defect clusters are considered to be the origin of brittle behavior in V–Cr–Ti alloys irradiated at low temperatures.