Classical superplasticity of SiAlON ceramics

Journal Article · Sun Jun 01 04:00:00 EDT 1997 · Journal of the American Ceramic Society

DOI:https://doi.org/10.1111/j.1151-2916.1997.tb02990.x· OSTI ID:512071

Rosenflanz, A; Chen, I W ^[1]

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1. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Materials Science and Engineering

Classical superplasticity of SiAlON ceramics with the nominal composition (Y{sub x}Li{sub y}){sub 0.6/(3x+y)}Si{sub 8.9}Al{sub 3.1}O{sub 2.5}N{sub 13.5} is reported in this study. During deformation, these materials exhibit little microstructural evolution, with negligible growth of elongated {beta}{prime}-phase grains and minimal texture formation. Excellent formabilities are obtained in the temperature range of 1,500--1,600 C in compression, where a strain rate of 10{sup {minus}2} s{sup {minus}1} has been achieved, and in punch stretching, where a strain rate of 1.2 {times} 10{sup {minus}3} s{sup {minus}1} has been used successfully. Flow stresses are found to be dramatically affected by the viscosity of the grain-boundary phase and decrease as the amount of lithium addition increases. Fracture stress also is compositionally dependent and decreases as the lithium content increases. As the overall formability is determined by the competition between fracture and deformation, maximum formability coincides with a maximum ratio of fracture stress to forming stress at an intermediate lithium composition. Finally, all materials exhibit higher room-temperature bend strength after postforming annealing. Thus, transient superplastic deformation does not impair the ultimate mechanical properties of the materials.

• Sponsoring Organization: Department of the Air Force, Washington, DC (United States)
• OSTI ID: 512071
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 6 Vol. 80; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM NITRIDES
ALUMINIUM OXIDES
DEFORMATION
LITHIUM OXIDES
MORPHOLOGICAL CHANGES
PHASE STUDIES
PLASTICITY
SILICON NITRIDES
SILICON OXIDES
YTTRIUM OXIDES