TEM STUDY OF HOT DEFORMATION EFFECTS ON (BI,PB)(2)SR2CA2CU3OX SILVER-SHEATHED TAPES

The microstructural effects of deformation at high temperatures on sil ver-sheathed (Bi,Pb)(2)Sr2Ca2Cu3Ox tapes have been studied by means of transmission electron microscopy. Hot deformation is found to cause b ending of the grains by introducing dislocations apparently without ge nerating cracks. Short-time deformation raises the dislocation density by one order of magnitude and yields higher dislocation densities com pared to long-time deformation. The observed dislocations mainly have 1/2[110] Burgers vectors and form irregular networks, both before and after the hot deformation. The significantly increased critical curren t density of hot deformed tapes can be explained by the introduction o f the observed defect structures, which are potential flux pinning sit es.