The Formation Mechanism of the Higher Performance V3Ga Phase on the High Ga Content Cu-Ga Compound/V Diffusion Reaction Through the High-Temperature XRD Analysis.

Abstract: V3Ga compound has a shorter radioactive decay time compared with Nb-based compounds and it will be one of the candidate superconducting magnet materials for advanced low activation fusion reactor systems.!Recently, we succeeded in developing new V3Ga wires, fabricated via the PIT process using high Ga content Cu-Ga compounds above Cu-Ga solid solution composition. Jc and Hc2 enhancements of V3Ga wire due to increasing three times of the V3Ga volume fraction were also confirmed. For the further microstructure control, in-situ observation of diffusion reaction with increase of temperature using High-Temperature X-ray diffraction (HT-XRD) was measured. Various high Ga content Cu-Ga compounds were composed with Cu3Ga (β phase: ∼30at%Ga), Cu9Ga4 (γ phase: ∼40at%Ga) and CuGa2 (δ phase: ∼64at%Ga) compounds. Especially, CuGa2 compound has much lower melting point (254°C) compared with various Cu-Ga compounds. In the case of diffusion reaction including CuGa2 phase, V3Ga phase was formed by the second step diffusion reactions; the first one is solid-liquid diffusion between the dissociated Ga liquid phase and metal V, the second one is soild-solid diffusion reaction between solid phase formed by the first step reaction and metal V [Copyright &y& Elsevier]