High strain warm extrusion and warm rolling of multifilamentary Bi-2223 metallic precursor wire

摘要

Multifilamentary Bi-2223 metallic precursor (MP) wires have been made using a combination of warm extrusion and warm rolling. Ram-type extrusions were used with a 90 mm diameter billet size. These could be extruded to very high reduction ratios R, up to R=800; the resulting long lengths of extrudates were directly spooled. To identify useful temperature zones for high strain deformation processing such as rolling, the compressive yield stress versus strain was measured as a function of temperature and strain rate. This was done for a multifilamentary extrudate, and for the matrix and MP materials individually. Using these optimal warm deformation parameters, MP extrudates with a wide variety in wire geometry, silver-to-filament ratio and filament dimensions, were warm rolled using 20-70