Superplastic deformation of Al2O3/Y-TZP particulate composites and laminates

Superplastic deformation of Al₂O₃/Y-TZP particulate composites and laminates

Jue Wang ^a, Eric M. Taleff ^a,b, Desiderio Kovar ^a,b,*

^a Materials Science and Engineering Program, The University of Texas at Austin, Austin, TX 78712, USA
^b Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78712, USA

Received 1 June 2004; received in revised form 4 August 2004; accepted 8 August 2004

Abstract
Al₂O₃/Y-TZP particulate composites and particulate laminates with varying compositions and ratios of layer thickness were fabricated by tapecasting, lamination, and sintering. Tensile strain-rate-change (SRC) tests were conducted on the particulate composites and particulate laminates at a temperature of 1350°C and compared to previous results where tests were conducted in compression. Stress exponents for particulate composites and laminates were measured to be approximately two in both tension and compression. The observed similarity of SRC data suggests that a common deformation mechanism exists in tension and compression. Elongation-to-failure tests were also conducted at 1350°C at a constant true-strain rate of 10^-4 s^-1. It was found that the elongation-to-failures of particulate laminates are lower than for particulate composites with similar overall compositions because of interlayer constraint in the particulate laminates which induces cavitation in the harder layer. The increase in flow stress from dynamic grain growth was used to determine that flow stress depends on grain size to approximately the 1.5 power. Elongations for fine grained particulate composites produced by pressureless sintering were similar to those described in the literature for hot-pressed particulate composites of similar composition, but with slightly coarser grain sizes.