Phase development and critical current density of Bi-2223 tapes fabricated by groove rolling

The powder-in-tube technique is the most widely used method for fabricating silver-clad Bi-2223 wires and tapes. In this method the silver biller containing the precursor material is transformed to the final shape using metallurgical deformation techniques such as wire drawing and flat rolling. In the present study, a modified version of the powder-in-tube technique was adopted where the silver biller was reduced in size by groove rolling instead of wire drawing. Microstructural analysis during the initial deformation stage revealed crack formation in the superconductor core. Stress conditions during groove rolling were analysed and appropriate changes were incorporated in the deformation process. After groove rolling the wires were flat rolled to a final thickness of 250 mu m. Subsequent thermomechanical treatment resulted in tapes with critical current density of approximate to 19 700 A cm(-2) (critical current of approximate to 40 A).