Production of superconducting Cu-Nb-Sn alloy by hot extrusion of rapidly solidified powder

A Cu sub 92.5 Nb sub 5 Sn sub 2.5 alloy has been rapidly quenched into a powder by ultrasonic gas atomization. The structure of the powder consists of finely dispersed Nb particles in a Cu--Sn matrix. The powder has been consolidated by hot extrusion at 650 deg C. The extrusion does not change the phases present in the material appreciably, but annealing for 100 h at 650 deg C causes a transformation of the Nb particles to Nb sub 3 Sn. The extruded material shows superconductivity. The critical temperature T sub c of the as-quenched alloys is 8.0K, but increases to 15.6K after annealing for 100 h at 923K. The upper critical magnetic field, H sub c2 , and critical current density, J sub c , were 3.4 kOe at 4.2K and 7.4 x 10 exp 5 Am exp --2 at zero applied field and 4.2K, respectively. The appearance of superconductivity is attributed to the proximity effect of the Nb sub 3 Sn phase particles which are sufficiently well distributed to satisfy the leak distance and the critical particle size. Graphs, Photomicrographs. 8 ref.--AA