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本文利用高温高压大变形扭转实验,对富铁橄榄石大变形情况下的动态重结晶和颗粒尺度变化的特点进行了实验观测分析。富铁橄榄石集合体由纯铁橄榄石Fa100和圣卡罗橄榄石Fa10混合物经人工合成得到,试件的几何形状为圆柱体,直径9.6mm,高度4.86mm。实验在常角速率条件下进行,温度为1473K,围压为300MPa,剪应力为72～99MPa,剪应变率为1.35×10-4～3.11×10-4s-1,累积剪应变为3.98。对变形后样品的微结构进行了光学和扫描电镜的观测分析,得到橄榄石颗粒随应变增加而产生动态重结晶的具体物理图像,由EBSD观测结果给出了晶格取向随外加应变增加而产生的变化过程,利用两种统计方法得到了颗粒尺寸随应变增加而变化的过程,探讨了橄榄石动态重结晶的微观机制。与已有三轴压缩、简单剪切以及圣卡罗橄榄石的扭转变形结果进行了对比分析,同时对实验结果在地球物理方面的应用进行了讨论。
In this paper, experiments on the characteristics of dynamic recrystallization and grain-size changes of ferro-olivine with large deformation are carried out by using the experiment of high temperature and high pressure with large deformation. The iron-rich olivine aggregate is obtained by artificial synthesis of a mixture of pure olivine Fa100 and sa-carol olivine Fa10, and the geometric shape of the specimen is a cylinder with a diameter of 9.6 mm and a height of 4.86 mm. The experiment was carried out under the condition of constant angular velocity. The temperature was 1473K, the confining pressure was 300MPa, the shear stress was 72 ~ 99MPa, the shear strain rate was 1.35 × 10-4 ~ 3.11 × 10-4s-1 and the cumulative shear strain was 3.98. The microstructure of the deformed sample was observed by optical and scanning electron microscopy to obtain the specific physical image of the olivine particles with dynamic recrystallization as the strain increased. The EBSD observations show that the lattice orientation increases with the increase of the applied strain The process of particle size changing with the increase of strain was obtained by two statistical methods. The microscopic mechanism of dynamic recrystallization of olivine was also discussed. Comparing with the existing triaxial compression, simple shear and torsional deformation of santolino olivine, the application of experimental results in geophysics is also discussed.