High-temperature deformation of Al₂O₃/Y-TZP particulate composites and particulate laminates

Al2O3/Y-TZP particulate composites consisting of 20 - 80 vol% Al2O3 and Al2O3/Y-TZP particulate laminates with varying composition and ratios of layer thickness were fabricated, respectively, by tapecasting, lamination, and sintering. The resulting particulate composites and particulate laminates were tested in compression and tension at 1300 - 1450oC over strain rates from 1.00 × 10-5 to 3.16 × 10-4 s-1. The high temperature behaviors of Al2O3/Y-TZP particulate composites and particulate laminates were characterized under conditions in which changes to the microstructure during testing were deliberately minimized. Results show that stress exponents are approximately two for both particulate composites and particulate laminates when tested in compression and tension, consistent with a grain-boundary sliding mechanism. Particulate laminates are stronger than particulate composites with the same overall composition due to the constraint imposed by the hard layer on the soft layer during the deformation. This hard layer dominates the resistance to deformation of the particulate laminates. A limited number of elongation-to-failure tests were also conducted at 1350oC at a true strain rate of 1.00 × 10-4 s-1. Although grain growth and cavitaton occurred during the elongation-to-failure tests, superplasticity was observed for Al2O3/Y-TZP particulate composites and particulate laminates. In addition, models of composite creep behavior were compared to the experimental data. A constrained isostrain model was found to provide a good prediction for the high- temperature deformation of Al2O3/Y-TZP particulate composites and particulate laminates.