Microstructural examination of irradiated and unirradiated V–4Cr–4Ti pressurized creep tubes

Microstructures of three pressurized tubes of V–4Cr–4Ti heat 832665 following irradiation in the Advanced Test Reactor at ∼300 °C to ∼5 dpa are examined and compared with thermal creep tubes tested at 700 and 800 °C. Irradiation creep response at 300 °C is found to be associated with dislocation development and may be affected by precipitation. Stress appears to encourage grain boundary migration during irradiation creep. Segregation of Cr to boundaries and Si behind boundaries was found to accompany the grain boundary migration. Thermal creep is probably due to dislocation climb influenced by TiO2 precipitation.