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Hydrogen defects in ??-Al2O3 and water weakening of sapphire and alumina ceramics between 600 and 1000??C - II. Mechanical properties

Acta Materialia

By:
, , , and
DOI: 10.1016/S1359-6454(99)00449-8

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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 ??-Al2O3 single crystals and polycrystals associated with hydrogen incorporation. Prior to deformation, ??-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 ??m) polycrystals, as a result of enhanced dislocation mobility. Flow stresses of fine-grained (3-5 ??m) 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.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Hydrogen defects in ??-Al2O3 and water weakening of sapphire and alumina ceramics between 600 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 Science Ltd
Publisher location:
United Kingdom
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Acta Materialia
First page:
1495
Last page:
1504
Number of Pages:
10