Clh. Thieme et al., GRAIN-SIZE REDUCTION IN NB3SN WIRE USING COMPOSITE POWDER-METALLURGY FILAMENTS WITH CU(SN) ARTIFICIAL PINNING CENTERS, Applied physics letters, 65(8), 1994, pp. 1042-1044
Cu(Sn) artificial pinning centers (APCs) were introduced into multifil
amentary Nb3Sn wire using powder metallurgy Nb+Cu rods. In the composi
te Nb+Cu filaments the Cu ribbons had a thickness of either 20 or 5 nm
before reaction. During the 600-degrees-C anneal the APCs enhanced th
e reaction rate and reduced the Nb3Sn grain size to <20 nm. The Cu con
centration in the filaments decreased. In 20% Cu-20 nm APC wires the c
ritical current density over the A15 area was 2250 A/mm2 at 12 T and 4
.2 K. Flux pinning increased strongly with decreasing field.