Deformation of Bi,Pb(2223) tapes with two axial rolling under longitudinal stress: influence on microstructure

The control of precursor density during the deformation process of Bi,Pb(2223) tapes is of vital importance in order to achieve good homogeneity of the filaments. Above a certain density, the ceramic grains cannot slide anymore during deformation, leading to an increased sausaging. Two axial rolling is known to yield a higher homogeneity among the filaments. However, the ceramic density reaches a relatively high level after a few deformation steps. Therefore, we used a new combination of two axial rolling and longitudinal tension, in order to control the density of the tapes. We present the evolution of density and degree of texture, both during the deformation process and after the heat treatment. Results clearly show an improvement in the control of microstructure resulting in higher critical current densities in tapes deformed under longitudinal tension compared to tapes deformed without stress. A correlation was established between the level of longitudinal tension and the transport jc.