MULTIPLE-PASS WARM EXTRUSION OF EXPLOSIVELY COMPACTED CERAMIC SUPERCONDUCTIVE (Y-BA-K-CU-O) METAL BILLETS/

The fabrication of silver-sheathed Y(Ba,K)(2)Cu3O7 superconducting rod s by explosive compaction and subsequent warm-plastic deformation, emp loying multiple-pass extrusion at 470 degrees C, is reported and discu ssed. The impurity phase content, as well as the superconductivity of the component, were carefully controlled by employing intermediate and post-processing heat-treatment in flowing oxygen. The characterizatio n of the extruded rod after every extrusion pass, indicates a progress ive microstructural refinement, leading to subsequent reduction of the porosity, closing of microcracks and enhancing the integrity of the m etal/ceramic interface. Evaluation of the mechanical properties of the ceramic core-material, e.g. microhardness and fracture toughness, ind icated significant improvement of the formability of the fabricated co mponent. The various phase-transformation and transition temperature, T-c changes are presented and discussed, with respect to the manufactu ring processes employed. Extruded rods, of 5 mm diameter and 50 mm len gth, are used as HTS conductors in a rotating electrical machine. (C) 1997 Elsevier Science Ltd.