Flat Cavities formed in TZP caused by Superplastic Deformations at High Strain-Rates and Their Effect on Elongation

Abstract

Cavitation in a superplastic 3Y-TZP pulled under different temperature and strain-rate conditions was analyzed by means of SANS techniques. In high strain-rate deformations, the formation of crack-like flat cavities with their flat surfaces lying roughly normal to the tensile axis was found, in addition to conventional cavities slightly elongated along the tensile direction having been frequently observed in superplastically deformed 3Y-TZP. Coalescence of the nearby crack-like flat cavities during the high strain-rate deformations gave rise to the generation of large brittle-like cracks, which led to an earlier fracture without apparent occurrence of necking. A mechanism for the formation of the flat cavities and their effect on the elongation are discussed.