Development of anisotropic microstructures by dynamic recrystallization in the crust and mantle

动态再结晶（DRX）是塑性变形过程中的循环形核和晶粒长大过程.采用随机形核长大模型研究了动态再结晶过程中晶粒尺寸分布的演化规律。由形核速率和长大速率导出表征特征晶粒尺寸和再结晶周期的标度关系。晶粒尺寸从初始分布演化到稳态分布，该稳态分布近似为对数正态分布。变形条件之间的普遍关系（即，应力和温度）和稳态晶粒尺寸的矿物恢复蠕变制定。在地幔地震各向异性研究中，DRX对结构（或晶格择优取向，LPO）发展的影响是一个重要的问题。由于具有“有利”取向的晶粒（软晶粒）比具有“不利”取向的晶粒（硬晶粒）具有更大的位错能，软晶粒通过晶界迁移被硬晶粒取代。因此，由结晶滑移产生的LPO由于晶粒生长而变弱或减少。相反，无应变形核与其宿主晶粒具有几乎相同的取向，因此形核将增强以软晶粒为主的LPO。对于DRX，上述两个端部构件之间的纹理是可能的

Dynamic recrystallization (DRX) is characterized by cyclic events nucleation and grain growth during plastic deformation. The evolution of grain size distribution in dynamic recrystallization was investigated by a stochastic model of nucleation-and-growth. Scaling relations representing characteristic grain size and recrystallization cycle were derived from nucleation rate and growth rate. The grain size evolve from an initial distribution to a steady-state one that is approximated by a lognormal distribution. A universal relation between deformation conditions (i.e., stress and temperature) and the steady-state grain size were formulated for recovery creep of minerals. The influence of DRX on texture (or lattice preferred orientation, LPO) development is an important issue in considering seismic anisotropy in the Earth mantle. Since a grain with 'favorable' orientation (soft grain) has larger dislocation energy than that with 'unfavorable' orientation (hard grain), soft grains are replaced with hard grains by grain boundary migration. Therefore, the LPO produced by crystalline slip becomes weak or diminished by grain growth. On the contrary, strain-free nuclei have nearly the same orientation as their host grains, hence nucleation would enhance the LPO dominated by soft grains. Textures between the above two end-members are possible for DRX