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 processed using flat rolling, “sandwich” rolling, and pressing methods for the intermediate mechanical deformation in powder-in-tube process. The results show that not only the density of the microcracks but also their distribution affect Jc. Rolled tapes have a higher density of microcracks than pressed 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 three cases, Jc reaches a maximum value at an optimal reduction rate.