Electric Current Dependence on Superplastic Tensile Flow in Tetragonal Zirconia Polycrystal Under a DC Field

Electric DC current dependence on the superplastic flow in densified, fine-grained tetragonal ZrO2 polycrystal was systematically investigated. An optimal current density for large tensile ductility existed; the maximum elongation of 135% was achieved under the current density of 250 mA∙mm-2 at a furnace temperature of 1000 oC and an initial strain rate of 1×10-3 s-1. Application of DC current decreased the flow stress, while that simultaneously accelerated the grain growth in tetragonal ZrO2 polycrystal. The reduced flow stress and improved ductility can be explained not only by Joule heating but also by enhanced atomic diffusion or accelerated grain boundary sliding.