Dislocation unpinning in single crystals of ceramic oxides

Book · Mon Jan 01 04:00:00 EST 1973

OSTI ID:4421627

Ritchie, I G

From 5th international conference on internal friction and ultrasonic attenuation in crystalline solids; Aachen, Germany (27 Aug 1973). A counterbalanced reed pendulum was used to investigate amplitude-dependent damping at low frequencies in Mg0 and sapphire under strain. Fresh dislocations introduced into neutron-irradiated and unirradiated single crystals were shown to produce large amplitude-dependent effects. The shape of the damping vs amplitude curve is sensitive to vibration conditioning and varies markedly with temperature. The results were interpreted using the Blair, Hutchison, and Rogers theory for the thermally assisted unpinning of very long dislocation-loop lengths. In this theory a generalized pinning force was introduced into the Teutonico, Granato, and Luecke model; it was assumed that the dislocation loops are of equal length. Results. for a given specimen are presented in a temperature-strain diagram which delineates flve regions of different damping behavior. The binding energy between the pinning agent and dislocation, the dislocation loop length, and asymptotic behavior of the force law between dislocation and pinning agent are estimated from the results. (GE)

• Research Organization: Atomic Energy of Canada Ltd., Pinawa, Manitoba
• NSA Number: NSA-29-003005
• OSTI ID: 4421627
• Country of Publication: Germany
• Language: English

Related Subjects

*MAGNESIUM OXIDES-- PHYSICAL RADIATION EFFECTS
*SAPPHIRE-- PHYSICAL RADIATION EFFECTS
AMPLITUDES
BINDING ENERGY
DAMPING
DISLOCATIONS
MAGNETIC FLUX
MECHANICAL VIBRATIONS
MONOCRYSTALS
N50130* --Metals
Ceramics
& Other Materials--Ceramics & Cermets--Properties
Structure & Phase Studies
NEUTRON BEAMS
STRAINS
TEMPERATURE DEPENDENCE