Abstract
Sapphire filament oriented within 2 1/2° of the crystallographic c-axis underwent creep by a mechanism other than slip on the basal planes at temperatures above 1600° C. There was a stress below which creep could not be detected; this decreased from 180 MNm−2 at 1600° C to 65 MNm−2 at 1800° C. The total tensile strain obtained never exceeded 5%. Fracture occurred during a linear stage of creep in which the stress exponent of the strain-rate was approximately 6. The creep mechanism appeared to be slip on {20¯2¯1} 〈01 T2〉 (morphological unit cell). A filament in which the c-axis lay at 6° to the filament axis deformed by localized basal slip. The accompanying local latice rotations produced fracture at a small overall strain, usually less than 0.5%. The results demonstrate extreme anisotropy of creep in sapphire crystals.
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Gooch, D.J., Groves, G.W. The creep of sapphire filament with orientations close to the c-axis. J Mater Sci 8, 1238–1246 (1973). https://doi.org/10.1007/BF00549338
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DOI: https://doi.org/10.1007/BF00549338