Microstructural evolutions and variations in mechanical properties of a fine-grained yttria stabilized tetragonal zirconia caused by superplastic deformations

Uniaxial tensile and compressive deformations of 3Y-TZP specimens were conducted under proper superplastic conditions and correlations among microstructural evolutions and variations in mechanical properties caused by the deformations were evaluated. The specimens were deformed superplastically to pre-determined various strains at temperatures from 1623 to 1773K with initial strain rates from 10(-4) to 10(-3) sec(-1). Then the variations in room temperature hardness and fracture toughness of the deformed specimens were examined in conjunction with the variations in grain aspect ratio and volume fraction of cavities. The cavitation behaviors are quite different in tension and in compression, whereas the strain dependence of the aspect ratios in tension and in compression are approximately symmetric with respect to the origin of the strain axis. The hardness of the deformed specimens decreases with the decrease in relative density of the specimens. The fracture toughness of the deformed specimens has a strong connection with the grain aspect ratio.