Superplasticity in Al{sub 2}O{sub 3}-ZrO{sub 2}-Al{sub 2}TiO{sub 5} ceramics
- Michigan Technological Univ., Houghton, MI (United States)
In order for ceramics to exhibit superplasticity, it has been shown that a stable grain size less than 1 {mu}m must be present and that like metals, grain growth either prior to or during deformation can result in a loss of superplasticity, e.g. an increase in grain size from 0.4 to 3 {mu}m resulted in a 5 fold increase in the flow stress of yttria stabilized zirconia during compression testing at 1,450 C. The primary use of superplastic ceramics is in the net shape forging of parts, where the closed die forging operation will result in a fully dense ceramic part with little, if any, machining. Since up to 80% of the cost of ceramic parts is attributable to machining cost it is of benefit to develop ceramics that are superplastic and resistant to grain growth. Grain growth in ceramics at high temperature occurs as a result of grain boundary migration where like grain boundaries are in contact, i.e. all grain boundaries in a single phase material such as zirconia. The addition of a second phase, e.g. alumina, has been shown to increase the extent of superplasticity and reduce the flow stress by reducing grain growth during deformation by reducing the number of like grain boundaries in contact. It is the authors` hypothesis that with the addition of a third, mutually insoluble phase, in this instance aluminum titanate, the number of like grain boundaries can be significantly reduced. The material will be more resistant to grain growth and maintain its superplastic behavior to higher strains than either the single or two phase ceramic alloys investigated to date.
- OSTI ID:
- 39888
- Journal Information:
- Scripta Metallurgica et Materialia, Vol. 32, Issue 7; Other Information: PBD: 1 Apr 1995
- Country of Publication:
- United States
- Language:
- English
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