Hydrogen defects in α-Al2O3 and water weakening of sapphire and alumina ceramics between 600°C and 1000°C: II. Mechanical properties
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Abstract
Hydrogen impurities in alumina have been introduced by hydrothermal annealing (see part I). In this paper, we report on reductions in the flow strength of α-Al2O3 single crystals and polycrystals associated with hydrogen incorporation. Prior to deformation, α-Al2O3 single crystal and ceramic specimens were annealed in the presence of supercritical water at 850° or 900°C, under 1500 MPa pressure. Sapphire and alumina ceramics were plastically deformed between 600° and 1000°C under 1500 MPa pressure, by the addition of a uniaxial stress. Flow stresses are reduced by a factor of two, due to the presence of water, for sapphire and large grain (30–50 μm) polycrystals, as a result of enhanced dislocation mobility. Flow stresses of fine-grained (3–5 μm) polycrystals are reduced by water by a factor of six. This large reduction in strength is attributed to a change in mechanism from dislocation glide under dry conditions to grain boundary sliding under hydrothermal conditions.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Hydrogen defects in α-Al2O3 and water weakening of sapphire and alumina ceramics between 600°C and 1000°C: II. Mechanical properties |
| Series title | Acta Materialia |
| DOI | 10.1016/S1359-6454(99)00449-8 |
| Volume | 48 |
| Issue | 7 |
| Year Published | 2000 |
| Language | English |
| Publisher | Elsevier |
| Contributing office(s) | Earthquake Science Center |
| Description | 10 p. |
| First page | 1495 |
| Last page | 1504 |
| Online Only (Y/N) | N |
| Additional Online Files (Y/N) | N |