Lattice preferred orientation in deformed-then-annealed material: observations from experimental and natural polycrystalline aggregates

In order to investigate the evolution of lattice preferred orientation (LPO ) obtained during deformation, we carried out post-deformational annealing experiments for rock analog materials, octachloropropane (C3Cl8) and norcam phor (C7H10O). Polycrystalline aggregates deformed at low-temperature/high- strain-rate conditions show complete obliteration of grain-boundary microst ructures (e.g., grainshape foliation) during annealing, but maintain the LP O by rapidly growing small grains which have inherited crystallographic ori entations from the adjacent old grains. On the other hand, polycrystalline aggregates deformed at high-temperature/low-strainrate conditions tend to m aintain deformation microstructures during annealing, due mainly to the pre sence of subgrain boundaries which pin the motion of grain boundaries. The limited mobility of grain boundaries also allows preservation of the LPO ob tained during deformation. During grain growth at the stage when textural e quilibrium is reached, polycrystalline aggregates show no preferential remo val of grains of certain crystallographic orientations. Therefore, our expe rimental results suggest that LPO obtained during deformation is insensitiv e to post-deformational annealing process. A microstructural analysis of na turally deformed-then-annealed quartzite indicates that the similar process es may operate in natural rocks.