Deformation of Superplastic Al{sub}2O{sub}3/Y-TZP Particulate and Particulate Laminate Composites

摘要

Particulate composites of Al{sub}2O{sub}3 and Y-TZP were some of the earliest and are still among the most successful superplastic ceramic composites. Superplastic Y-TZP is required in Al{sub}2O{sub}3/Y-TZP particulate composites to retain fine grain sizes in the Al{sub}2O{sub}3 phase, which normally coarsens at elevated temperatures. However, the high cost of Y-TZP relative to Al{sub}2O{sub}3 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 Al{sub}2O{sub}3/Y-TZP 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.