The effect of powder metallurgy Cu(Sn) APCs on grain size reduction and flux pinning in Nb/sub 3/Sn wire

Cu artificial pinning centers (APCs) measuring 20 or 5 nm across were introduced to Nb/sub 3/Sn and Nb/sub 3/Sn(Ta) wire by means of powder metallurgy. The APCs increased the filament hardness by less than 10%. Stress anneals could be applied without affecting the Cu APC content or morphology. The Cu APCs led to a fine grained Nb/sub 3/Sn, with an average grain size of 18 nm. The critical current over the filament area was 2250-2600 A/mm/sup 2/ at 12 T, virtually similar for the 20 and 5 nm APC wires. The Cu APCs improved reaction kinetics. >