THE BULK PROCESSING OF 2223-BSCCO POWDERS .2. TAPE ROLLING

The anisotropic mechanical properties of densified BSCCO (Bi-Sr-Ca-Cu- O) powders are of paramount importance during thermo-mechanical proces sing of superconducting tapes and wires. Maximum current carrying capa city requires both high relative density and a high degree of alignmen t of the BSCCO single crystal's superconducting planes parallel to the plane of the tape. This is also a configuration that causes high stre sses during compressive (i.e. powder compaction) deformation processin g. These high stresses can lead to cracking and thus degrade the condu ctive properties of the tape. In Part I of this work, we outlined some of the basic phenomenology of such powders under confined channel die compression. In this part we report results from a detailed finite el ement analysis of the tape rolling environment. We calculate both pres sures and shear strains in the core of oxide powder-in-tube (OPIT) pro cessed tapes. Rod-in-tube processing is investigated, as well as rolli ng with extra packing material. The calculated deformations were then applied as boundary conditions to the detailed micromechanical model d eveloped in Part I. The goal here was to understand the deformation en vironment in the core of a rolled OPIT workpiece and how this environm ent affects the microstructural evolution of the BSCCO powder. Such mi crostructures, in turn, have significant effects on the macroscopic ph enomenology of the core, and thus on the success of the processing. Ou r calculated results are used in order to help interpret a set of prot otypical rolling experiments which have been designed specifically for the purpose of investigating core morphologies as a result of various rolling environments.