Transmission Electron Microscope Study of the Dislocations in Plastically Deformed Synthetic Quartz

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Abstract
Transmission electron microscopy has been used to study the dislocations associated with the plastic deformation and recovery of single crystals of synthetic quartz. The crystals were deformed in compression at a constant strain rate under confining pressure over the temperature range 300 to 900°C. At 300°C rapid work‐hardening occurs due to the development of a high uniform density of tangled dislocations. The dislocation substructures which are produced during deformation at higher temperatures correspond closely to the substructures which develop on annealing a work‐hardened crystal. There is evidence that the rate of this recovery is strongly dependent upon the concentration of hydrogen present due to the influence of this impurity on dislocation climb. It is suggested, therefore, that the well‐established hydrolytic weakening of quartz occurs when the rate of recovery exceeds the rate of work‐hardening. This hypothesis predicts the observed variation of the hydrolytic weakening temperature with hydrogen concentration, strain rate, and crystal orientation.