Dislocation creep regimes in quartz aggregates

  • Hirth G
  • Tullis J
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Abstract

Using optical and TEM microscopy we have determined that three regimes of dislocation creep occur in experimentally deformed quartz aggregates, depending on the relative rates of grain boundary migration, dislocation climb and dislocation production. Within each regime a distinctive microstructure is produced due primarily to the operation of different mechanisms of dynamic recrystallization. At lower temperatures and faster strain rates the rate of dislocation production is too great for diffusion-controlled dislocation climb to be an effective recovery mechanism. In this regime recovery is accommodated by strain-induced grain boundary migration recrystallization. With an increase in temperature or decrease in strain rate, the rate of dislocation climb becomes sufficiently rapid to accommodate recovery. In this regime dynamic recrystallization occurs by progressive subgrain rotation. With a further increase in temperature or decrease in strain rate dislocation climb remains sufficiently rapid to accommodate recovery. However, in this regime grain boundary migration is rapid, thus recrystallization occurs by both grain boundary migration and progressive subgrain rotation. The identification of the three regimes of dislocation creep may have important implications for the determination of flow law parameters and the calibration of recrystallized grain size piezometers. In addition, the identification of a particular dislocation creep regime could be useful in helping to constrain the conditions at which a given natural deformation has occurred. © 1992.

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Authors

  • Greg Hirth

  • Jan Tullis

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