FRACTURE AND TWINNING IN SAPPHIRE (ALPHA AL2O3 CRYSTALS)
AEROSPACE CORP EL SEGUNDO CA
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The fracture behavior of 60 degree oriented sapphire crystals was investigated for both tension and compression. Plastic flow on the basal plane was found to be a factor in reducing the tensile stress required to produce fracture in the temperature range 1100 to 1500 C. Mechanical twins, both 0001 and 0111 types, were produced by compression in the temperature range 1100 to 1300 C. Cracks propagated more readily along the twin boundaries than in the nontwinned crystal.