Superplasticity in Al 2O 3-20vol% spinel (MgO · 1.5Al 2O 3) ceramics

Abstract

Superplasticity in Al 2O 3-20 vol% spinel (MgO · 1.5Al 2O 3) is investigated by means of tensile testing in the temperature range 1300–1550 °C. The dispersion of spinel phase in Al 2O 3 slightly reduces the flow stress, and highly enhances the high-temperature ductility at the same stress level in comparison with 0.1 wt% MgO-doped single-phase Al 2O 3. A maximum elongation of 396% is obtained at 1550 °C and a strain rate of 2.4 × 10 −4s −1. The flow stress reduction is associated with a slight reduction in activation energy for superplastic flow. The extensive ductility in Al 2O 3-20 vol% spinel cannot be explained only from the stress reduction. The Al 2O 3/spinel boundaries are expected to have much larger resistance to crack extension than Al 2O 3 grain boundaries.