Advances in Superplasticity and Superplastic Forming
Edited by E.M. Taleff, P.A. Friedman, P.E. Krajewski, R.S. Mishra and J.G. Schroth
TMS (The Minerals, Metals & Materials Society), 2004

Deformation of Superplastic Al₂O₃/Y-TZP Particulate and
Particulate Laminate Composites

Jue Wang ¹, Desiderio Kovar ^1,2 and Eric M. Taleff ^1,2

1. The University of Texas at Austin, Materials Science and Engineering Program,
   1 University Station, C2201, Austin, TX 78712-0292.
2. The University of Texas at Austin, Department of Mechanical Engineering, 1 University
   Station, C2200 Austin, TX 78712-0292.
   Abstract
   
   Particulate composites of Al₂O₃ and Y-TZP were some of the earliest and are still among the most successful superplastic ceramic composites. Superplastic Y-TZP is required in Al₂O₃/Y-TZP particulate composites to retain fine grain sizes in the Al₂O₃ phase, which normally coarsens at elevated temperatures. However, the high cost of Y-TZP relative to Al₂O₃ provides incentive to understand the effect volume fraction has on deformation behavior of this composite system in order to engineer composites which minimize the expensive Y-TZP phase while achieving desired behaviors. To this end, a number of particulate and particulate laminate Al₂O₃ composites have been investigated over a range of compositions. These composites were mechanically tested over a range of strain rates at a temperature of 1350°C. Particulate laminate composites were tested in compression for both isostress and isostrain orientations and were tested in tension for the isostrain orientation. A constrained isostrain model is found to best describe, among current models, the behaviors of both particulate composites and particulate laminate composites tested in either the isostress or isostrain orientations. The similarity in behaviors between particulate laminates in the isostress and isostrain orientations is attributed to layer constraint, which enables the strongest layer to dominate deformation behavior.