Member, American Ceramic Society.
Constrained Densification of Alumina/Zirconia Hybrid Laminates, I: Experimental Observations of Processing Defects
Article first published online: 20 JAN 2005
Journal of the American Ceramic Society
Volume 80, Issue 8, pages 1929–1939, August 1997
How to Cite
Cai, P. Z., Green, D. J. and Messing, G. L. (1997), Constrained Densification of Alumina/Zirconia Hybrid Laminates, I: Experimental Observations of Processing Defects. Journal of the American Ceramic Society, 80: 1929–1939. doi: 10.1111/j.1151-2916.1997.tb03075.x
R. K. Bordia—contributing editor
Supported by the Center for Advanced Materials at The Pennsylvania State Uni-versity.
- Issue published online: 20 JAN 2005
- Article first published online: 20 JAN 2005
- Manuscript No. 191746. Received June 14, 1996; approved January 21, 1997.
Various forms of damage were observed in pressure-less-sintered Al2O3/ZrO2symmetric laminates and asymmetric laminates (bilayers) fabricated by tape casting and lamination. These defects included channel cracks in the ZrO2 layers, Al2O3 edge-effect cracks parallel to the layers, delamination in the Al2O3layers, and debonding between the Al2O3and ZrO2layers. Based on detailed microscopic observations, the defects were attributed to sintering rate and thermal expansion mismatch between the layers. Cracks or cracklike defects were formed in the early stages of densification, and these cracks either opened during sintering or acted as preexisting flaws for thermal expansion mismatch cracks. Consequently, the extent of cracking could be reduced or even eliminated by decreasing mismatch stresses during the sintering and cooling stages. This can be accomplished by reducing the heating and/or cooling rates or by adding Al2O3in the ZrO2layers. The sintering mismatch stresses were estimated from the degree of curling in asymmetric laminates and from layer viscosities that were obtained by cyclic loading dilatometry. The measured curvature was an indication of the mismatch in sintering strain between Al2O3and ZrO2and were consistent with the dilatometric data that were obtained for the component layers.