EFFECTS OF INITIAL COLD WORK CONDITIONS ON THE DEFORMATION AND CURRENT CAPACITY OF MONOFILAMENTARY AND MULTIFILAMENTARY BI-2223 CONDUCTORS

The influences of initial cold work conditions on the deformation char acteristics and the current-carrying capability of Bi-2223 powder-in-t ube conductors have been investigated by varying the working friction and the amount of reduction per pass. The results demonstrate that def ormation of the conductors can be very inhomogeneous depending on the working parameters. Specifically, dead zones are found within the tran sverse cross-sections of the tapes close to the tools-sample interface s such that the bulk of the deformation is restricted to the central p ortions of the conductors. Since the core of monofilamentary tape is l ocated outside the dead zones, it is highly densified when deformed un der high friction condition resulting in the largest J(c). On the othe r hand, a large number of filaments in multifilamentary tape reside wi thin the dead zones such that high working friction does not result in optimum J(c). Instead, a combination of low friction and large reduct ion per pass resulted in the most homogeneous deformation and highest current capacity.