Effect of internal stress disturbance on the stress-induced transformation toughening of an alumina/zirconia dual-phase composite

Abstract

The toughening and strengthening of a dual-phase composite, consisting of alpha-alumina (α-Al₂O₃) and tetragonal-zirconia (t-ZrO₂), were investigated. The toughness of the composite was evaluated through the precise measurement of work-of-fracture (WOF), which is a measure of total fracture resistance involving the rising R-curve effect. It was found that both the WOF and flexural strength of the composite were maximized at a t-ZrO₂ volume fraction f _Z of about 0.7. The thermal degradation of the mechanical properties was also observed. The effect of the internal stresses arising from the thermoelastic mismatch between α-Al₂O₃ and t-ZrO₂ on the critical stresses of the reversible phase transformation of t-ZrO₂ was numerically examined to describe the f _Z - and temperature-dependencies of WOF quantitatively.

Acknowledgements

The authors wish to thank Professor K. Wakashima of Tokyo Institute of Technology and Professor B. P. Kashyap of Indian Institute of Technology Bombay for helpful discussions on this subject.