Magneto-optical images of Ag/Bi-2223 tapes processed by flat rolling, "sandwich" rolling and pressing

Magneto-optical imaging (MOI) has been used for study Ag/Bi-2223 tapes proc essed using net rolling, "sandwich" rolling, and pressing methods for the i ntermediate mechanical deformation in powder-in-tube process. The results s how that not only the density of the microcracks but also their distributio n affect J(c). Rolled tapes have a higher density of microcracks than press ed tapes. Although the flat rolled tape and "sandwich" rolled tape have the same level density of microcracks at the same reduction, the cracks in the former are more in the transverse direction than in the latter. In all thr ee cases, J(c) reaches a maximum value at an optimal reduction rate.