Powder metallurgy processed Nb3Sn employing extrusion and varying Nb content

Extension of powder metallurgy (P/M) processing of Cu-Nb-Sn is described for small scale industrial uniaxial extrusion (
R \leq 10^{4}
) and for small scale hydrostatic extrusions for areal reductions R = 2000. Successful 2.5 cm o.d. uniaxial P/M processed extrusions at 950 and 250°F were obtained. Model cold hydrostatic extrusions of single tin core and multitin core wire are described. The effect of Nb content for Cu-x wt% Nb, where
36 \leq \times \leq 60
was examined. Increased over-all critical current densities, J
c
were obtained with increased Nb content up to 50 wt% Nb. For proper comparisons, values of J
cm
(where the prestress is removed), are given for several compositions. Improvement in J
c
for
T \leq 4.2
K is also presented. Incorporation of Tl in Nb
3
Sn by means of Sn-Ti core processing results in further increases in J
c
. The low R and large initial powder sizes result in relatively thick Nb fibers which are not completely reacted. The present extrusion P/M processed wires demonstrate several practical approaches for development of high performance materials. Optimization should yield high values of J
c
at 20 tesla.