Effect of Fast Neutron Irradiation on the Microstructure in Particle Dispersed Ultra-fine Grained V-Y Alloys

Abstract

An alloy having ultra-fine grains with dispersed particles is expected to have the resistance of irradiation embrittlement. We examine the microstructures of V-1.6 and 2.6Y alloys, having ultra-fine grains with dispersed particles, after neutron irradiation at temperatures between 290 and 800 C. The grain size was the level of a few hundreds of nanometers, and the size in diameter of V-2.6Y alloy was much smaller than that of V-1.6Y alloy, where the irradiation did not change the size. The number density of particles in V-2.6Y alloy was higher than that in V-1.6Y alloy. Voids were formed only at 290 C, where the number density of voids in V-2.6Y alloy was smaller than that in V-1.6Y alloy. The void formation was efficiently suppressed due to fine-grains and dispersed particles.

High temperature strength of fine-grained, particle-dispersed V–(1.7–2.4)wt%Y alloys with different grain sizes and particle densities

“…For vanadium the authors proposed a powder-metallurgical process to reduce grain size associated with finely dispersed particles and ensure good ductility of vanadium by removing solute oxygen and nitrogen from the matrix [11]. By applying the process, they developed V-Y alloys with very fine grains and dispersed particles of Y 2 O 3 and YN and demonstrated that the alloys show a good ductility and strength even in the condition of no plastic working after HIP [12] and are resistant to fast neutron irradiation at temperatures from 563 to 1073 K up to 0.25-0.7 dpa [13,14].…”

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

“…Y 2 O 3 particles were formed only in the fine grains as indicated by arrows in (b). Although X-ray diffractometry [13] showed that both Y 2 O 3 and YN existed in the alloy, Y 2 O 3 were only observed in the TEM [14]. The particles observed in this paper were considered as Y 2 O 3 .…”

“…Since the volume fraction of particles increased after irradiation, additional nucleation of particles occurred. Since free yttrium is expected to exist in the fine grain before irradiation [14], oxygen introduced from the surrounding during irradiation would combine with yttrium to nucleate Y 2 O 3 particles. Voids were not observed in both grain regions.…”

High Temperature Deformation of a Fine-Grained and Particle-Dispersed V-2.3%Y-4%Ti-3%Mo Alloy

“…[5][6][7][8][9] The fabricated alloys were confirmed to exhibit good resistance against neutron irradiation to 0.25 and 0.60 displacement per atom (dpa) at 563 and 873 K. 6,10,11) In addition, the alloys showed a stable microstructure for annealing up to 1573 K and good ductility in the HIPed and annealed state (no plastic working) that is due to a solute (oxygen and nitrogen) free V matrix phase. [6][7][8] Regarding the high temperature strength of the fabricated alloys it was found that up to around 1023 K V-(1.7-2.4)Y (in mass%) alloys exhibited higher strengths than V-4Cr-4Ti (Nifs heat-1), 3,12) however above 1173 K the alloys showed lower strengths than a solution hardened V-4Cr-4Ti.…”