GENERAL RESEARCH: MECHANICAL BEHAVIOR OF SAPPHIRE
AEROSPACE CORP EL SEGUNDO CA
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The present state of our knowledge on the mechanical behavior of sapphire is reviewed Sapphire deforms plastically at temperatures above 900 C, the most common mode of deformation being slip on the basal plan in the 1120 direction. However, under certain conditions, slip may occur on prism planes or twinning may occur. A yield point is often observed. This appears to be related to the multiplication of dislocations by a mechaninism which is controlled by the motion of dislocations through the lattice, rather than by the tearing of dislocations from an impurity or defect atmosphere. The dynamics of yielding and flow is similar and can be expressed by either of two thermally activated equations. In one, the effect of stress is principally on the pre- exponential frequency factor in the other, its effect is principally on the activation energy.
- Geology, Geochemistry and Mineralogy