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

The control of precursor density during the deformation process of Bi,Pb(22 23) tapes is of vital importance in order to achieve good homogeneity of th e filaments. Above a certain density, the ceramic grains cannot slide anymo re during deformation, leading to an increased sausaging. Two axial rolling is known to yield a higher homogeneity among the filaments. However, the c eramic density reaches a relatively high level after a few deformation step s. Therefore, we used a new combination of two axial rolling and longitudin al tension, in order to control the density of the tapes. We present the ev olution of density and degree of texture, both during the deformation proce ss and after the heat treatment. Results clearly show an improvement in the control of microstructure resulting in higher critical current densities i n tapes deformed under longitudinal tension compared to tapes deformed with out stress. A correlation was established between the level of longitudinal tension and the transport jc.