Effects of residual stresses on mechanical properties of three-layer alumina-based composites

Journal Article · Fri Feb 19 04:00:00 EST 1999 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(98)00464-3· OSTI ID:335287

She, J H ^[1]; Scheppokat, S; Janssen, R; Claussen, N ^[2]

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1. Osaka National Research Inst., Ikeda, Osaka (Japan). Dept. of Energy Conversion
2. Technische Univ. Hamburg-Harburg, Hamburg (Germany). Advanced Ceramics Group

It is well known that the mechanical properties of ceramic components for structural applications can be enhanced by the introduction of surface compressive stresses during fabrication. For alumina ceramics, this goal can be attained by incorporating a second phase such as mullite into the surface region. Due to the mismatch of thermal expansion coefficient between mullite and alumina, a residual surface compressive stress will be created during cool-down after heat-treatment. Recently, an increase of 50--150% in fracture toughness has been obtained in the experiment by making a three-layer alumina composite in which the outer layers contain 40 vol% mullite. In other experiments where mullite was formed in the surface region by heating alumina in a bed of SiC powder or by annealing an Si-deposited alumina in air, the strength increases of > 25% have also been reported. These increases are attributed to the presence of surface residual compressive stresses. The existence of residual surface stresses can be confirmed by X-ray diffraction. The purpose of this work is to show that the X-ray diffraction technique can be used to determine the residual stresses in the layers of three-layered composites, and that the mechanical properties are closely related to the magnitudes of the residual stresses.

• OSTI ID: 335287
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 6 Vol. 40; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
COMPOSITE MATERIALS
LAYERS
MECHANICAL PROPERTIES
MULLITE
RESIDUAL STRESSES
X-RAY DIFFRACTION
ZIRCONIUM OXIDES