The effect of static annealing on microstructures and crystallographic preferred orientations of quartzites experimentally deformed in axial compression and shear

Abstract

Abstract Quartzite samples were experimentally deformed with partial to complete dynamic recrystallization by axial compression (strain magnitude of 0.8 to 1.4) and by general shear (strain magnitude of 1.3 to 2.8) in each of the three dislocation creep regimes, and subsequently annealed with complete static recrystallization at the deformation temperature for 120 hours. The c -axis crystallographic preferred orientation (CPO), 3D grain size distribution, grain boundary surface shape, and misorientation density were measured before and after annealing. The effect of annealing on the CPO was minor, but the microstructure was greatly changed. All of the annealed samples were completely recrystallized. The recrystallized grain size increased by a factor of 2 to 5, and was greatest for samples deformed at lowest temperature. The grain boundary lobateness (PARIS factor) and misorientation density were reduced significantly. The CPOs for all the deformed samples were relatively unchanged by annealing, although the strengths are somewhat decreased; for sheared samples the asymmetry was preserved. The results suggest microstructural criteria for recognizing the occurrence of static annealing and for estimating the dynamically recrystallized grain size relevant for paleopiezometry from annealed samples.