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High-strain-rate superplasticity in oxide ceramics

Authors
Publisher
Elsevier Ltd
Publication Date
Volume
8
Identifiers
DOI: 10.1016/j.stam.2007.09.006
Keywords
  • Superplasticity
  • High-Strain Rate
  • Grain Growth
  • Diffusion
  • Stress Relaxation
  • Cavitation

Abstract

Abstract Factors limiting the strain rate of superplastic deformation in ceramic materials are discussed on the basis of existing models and experimental results concerning high-temperature plastic deformation, intergranular cavitation and dynamic grain growth. From the discussion, it is indicated that simultaneously fulfilling the following conditions is essential for attaining high-strain-rate superplasticity (HSRS) in ceramic materials: reduction in the initial grain size, enhanced diffusivity, suppressed dynamic grain growth, a homogeneous microstructure and a reduced number of residual defects. In the light of these conditions, explanations are given for HSRS attained in earlier studies on some oxide materials. It is also shown that HSRS can be intentionally attained in doped yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and composites synthesized from ZrO 2, Al 2O 3 and MgO 2; the tensile ductility of these composites reached 300–2500% at a strain rate of 0.01–1.0 s −1. The postdeformation microstructure indicates that some secondary phases may suppress cavitation damage and thereby enhance HSRS.

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