Bronze for superconducting wires: The powder metallurgy approach

Present methods for making high tin content bronze, suitable for use in superconductor wire, have proven difficult to scale up for production of large diameter billets. An homogeneous, fine grain size bronze is essential for fabrication of ultrafine filament Nb3Sn composite wires, using the bronze process. A method for producing uniform powders by forced convective cooling of molten particles has made possible a uniform bronze powder, which can be formed into a billet by powder metallurgy techniques. Test billets, made by vacuum hot pressing the rapidly solidified powders inside containers, were examined for homogeneity, grain size, and compaction. As compared to vacuum or continuously cast bronzes, improvements in homogeneity and grain size were found for powders hot pressed for 2-4 hours at 500-700°C.