Liquid phase sintering and the use of Nb-H powder for preparing Cu-Nb3Sn wires

Cu-Nb3Sn wires were prepared by the liquid phase sintering method. A Nb-H powder was used instead of the conventional and more expensive pure Nb powder. The pressed ingot of Cu-30wt%(Nb-H)-0.3wt%Al was degassed and heat treated under vacuum in the region of Cu liquid phase (T = 1200°C). The hydrogen released during the process acts as a reducing atmosphere, and also as an activation agent promoting the wetting between liquid copper and niobium, leading to soft, highly dense Cu-Nb sintered samples. Tin diffusion and reaction were made by external and internal processes. In the latter case cores of tin rich alloy were used, and the occurrence of hard η-phase precipitates was identified. The critical temperature is in the range of 16.0 ∼ 16.8K, and the critical current density is around 10⁵A/cm²at H = 7T.