APPLICATION OF CRYSTAL PLASTICITY THEORY FOR MECHANICALLY PROCESSED BSCCO SUPERCONDUCTORS

Mechanical processing of superconducting oxides leads to the fabrication of high J(c) superconducting tapes and wires. The best conducting properties (high J(c)) hinge upon the achievement of a high degree of densification, sharp crystallographic textures characterized by the conducting crystallographic planes parallel to the plane of the conducting tape or to the axis of the conducting wire, and the minimum possible density of microcracks whose plane faces intersect the direction of current flow. In this study, we investigate the crystallographic texture evolution in compressed 2223 BSCCO powders. Our mechanical models are intended to model thermomechanical processing by rolling. We simulate texture evolution using three different models: the constrained hybrid (CH), the Sachs, and the self-consistent (S-C) models. In all of these, elasticity is neglected and crystallographic shearing is the only mechanism assumed to cause inelastic deformation. Predictions of the three models are discussed and compared to existing experimental results for axisymmetric and plane strain compression of 2223 BSCCO powders. To account for shear strains involved in the rolling process, we assume simple boundary conditions which consist of adding a simple shear component on the velocity gradient to the plane strain conditions. The predicted results for rolling are compared to plane strain compression results.