Grain- to multiple-grain-scale deformation processes during diffusion creep of forsterite + diopside aggregate: 1. Direct observations
Grain- to multiple-grain-scale deformation processes during diffusion creep of forsterite + diopside aggregate: 1. Direct observations
复制标题
镁橄榄石透辉石集合体扩散蠕变过程中的颗粒到多颗粒尺度变形过程：1.直接观察
DOI：
10.1002/2017jb014254
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发表时间：
2017
影响因子：
--
通讯作者：
T. Hiraga
中科院分区：
文献类型：
--
作者：
G. Maruyama;T. Hiraga
我们在扩散蠕变状态下单轴变形细粒（~ 1 μm）镁橄榄石+透辉石（5和20体积%）聚集体。在变形之前，在圆柱形样品的侧表面上研磨线标记，以检测单颗粒至多颗粒尺度的变形。我们在相同样本上多次冷却后对标记蚀刻表面进行了变形实验和观察。从平行于压缩轴的标记物的宏观缩短以数十个晶粒的尺度测量的应变与样品的总应变一致。然而，在显微镜下，标记强烈分割和旋转的晶粒尺度增加与样品应变。同时，在大多数样品中，基本上没有观察到晶粒内的变形。表面微观结构，包括标记的变形，揭示了晶界迁移，晶界滑动，刚体晶粒旋转和晶粒邻居切换的系列操作，这些操作与扩散控制超塑性中预期的过程很好地对应。这一序列是常见的两个样品组成的镁橄榄石晶粒的板状和等轴晶粒形状，已被证明发展显着的结晶择优取向（CPO）和随机（或弱）CPO，分别在扩散蠕变。在变形机制从扩散蠕变到位错蠕变之间的过渡附近的应力下变形的试样中相对较大的镁橄榄石晶粒的晶内区域揭示了标记变形和表面折痕和亚晶界的形成，这表明晶内位错过程。表面微观结构较好地反映了材料的变形状态。
We uniaxially deformed fine‐grained (~ 1 μm) forsterite + diopside (5 and 20 vol %) aggregates in the diffusion creep regime. Prior to deformation, line markers were milled on a lateral surface of a cylindrical sample to detect single‐ to multiple‐grain‐scale deformation. We performed deformation experiments and observations of the marker‐etched surface after sample cooling multiple times on the same specimens. The strain measured at the scale of several tens of grains from macroscopic shortening of the markers parallel to the compression axis is consistent with the total strain of the sample. However, microscopically, the markers are intensely segmented and rotated at the grain scale increasing with the sample strain. Meanwhile, essentially, no deformation is observed within the grains in most of the samples. The surface microstructures, including the deformation of the markers, reveal the serial operations of grain boundary migration, grain boundary sliding, rigid body grain rotation, and grain neighbor switching, which correspond well to processes expected in diffusion‐controlled superplasticity. This sequence is commonly observed in both samples consisting of forsterite grains of tabular and equiaxed grain shapes, which have been shown to develop notable crystallographic preferred orientation (CPO) and random (or weak) CPO, respectively, during diffusion creep. Intragranular regions of relatively larger forsterite grains in the specimens deformed at stresses near the transition between deformation mechanisms from diffusion creep to dislocation creep reveal marker deformation and formation of surface creases and subgrain boundaries, which indicate intragranular dislocation processes. Overall, the surface microstructures reflect the deformation state of the materials well.