Effect of neutron irradiation on the microstructure and hardness in particle dispersed ultra-fine grained V–Y alloys

Effects of neutron irradiation on the microstructure and hardness in V–1.6 and 2.6Y (mass%) alloys were studied. The alloys consisted of both fine grains of a few hundreds of nanometers in diameter with finely dispersed particles and small amounts of coarse grains of a few micrometers in diameter without dispersed particles. The microstructures after neutron irradiation at 290 and 800 °C to 0.25 and 0.7 dpa, respectively, were examined with transmission electron microscopy. Irradiation did not change the grain size. Interstitial loops and voids were formed in the coarse grains irradiated at 290 °C, while voids were formed only in the fine grains. The number density of voids decreased with decreasing grain size. Interstitial loops and voids were not observed in V–1.6Y alloy irradiated at 800 °C, while thin plates were formed only in the coarse grains. The formation of interstitial loops and voids was efficiently suppressed in the fine grains.