Hot Extrusion of Ceramics

Two dense ceramics, Bi₂Sr₂CaCu₂O_{8+ X} and 2Y-TZP: 10 wt% Al₂O₃, were hot-extruded through conical dies under a wide range of conditions. Extrusion of Bi₂Sr₂CaCu₂O_{8+ X} was performed at 775° to 825°C and speeds of 0.0005 to 0.2 mm/s, with the die semi-angles from 30° to 60° and extrusion ratios from 4 to 9. Extrusion of 2Y-TZP:10 wt% Al₂O₃ was performed at 1650°C and 0.017 mm/s. During hot extrusion of Bi₂Sr₂CaCu₂O_{8+ X} , a strong texture was developed with the basal plane aligned along the extrusion direction, whereas the zirconia/alumina composite underwent grain growth which resulted in strain hardening. A simple analytical extrusion model for strain-rate-sensitive materials has been developed using a combined slab method and upper-bound method and a power-law material flow equation. The model predictions are in good agreement with the experimental results and they further serve to delineate the limitation of the extrusion technique for ceramic applications.