Slip and twinning in sapphire ([alpha]-Al[sub 2]O[sub 3])

Journal Article · Mon Jan 31 23:00:00 EST 1994 · Journal of the American Ceramic Society; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1994.tb07006.x· OSTI ID:7207498

Lagerloef, K P.D.; Heuer, A H ^[1]; Castaing, J; Riviere, J P ^[2]; Mitchell, T E ^[3]

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1. Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Materials Science and Engineering
2. CNRS Bellevue, Meudon (France). Lab. Physique des Materiaux
3. Los Alamos National Lab., NM (United States). Center for Materials Research

The plastic deformation of sapphire ([alpha]-Al[sub 2]O[sub 3]) has been studied under hydrostatic confining pressure at temperatures below the ambient pressure brittle-to-ductile transition temperature. Samples oriented for prism plane slip (Type 1 samples) were deformed via dislocation slip at temperatures as low as 200 C. Samples oriented for basal slip (Type 2 samples) could be plastically deformed at temperatures as low as 400 C but showed more complicated deformation behavior, inasmuch as the sample orientation also allowed for the activation of basal twinning and two of the three rhombohedral twin systems. The temperature dependence of the critical resolved shear stress for basal slip was significantly greater than that for prism plane slip, causing the latter system to be the easy slip system below [approximately] 600 C. Type 2 samples deformed primarily by basal twinning in preference to both rhombohedral twinning and basal slip. The different temperature dependence of shear stress for basal and prism plane slip is attributed to details of the dislocation core structure; prism plane dislocations, having a large Burgers vector can dissociate into three collinear partials separated by relatively low-energy stacking faults, whereas the comparable dissociation of basal dislocations produces two noncollinear partials separated by a relatively high energy stacking fault. Thus, dissociation of basal dislocations is most likely restricted to the dislocation core, which is manifested in a higher Peierls stress at low temperatures for basal slip compared to prism plane slip.

• OSTI ID: 7207498
• Journal Information: Journal of the American Ceramic Society; (United States), Journal Name: Journal of the American Ceramic Society; (United States) Vol. 77:2; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
CORUNDUM
DEFORMATION
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
SAPPHIRE
SLIP
TWINNING