High‐temperature creep of forsterite single crystals
High‐temperature creep of forsterite single crystals
复制标题
镁橄榄石单晶的高温蠕变
DOI：
10.1029/jb086ib07p06219
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发表时间：
1981
影响因子：
--
通讯作者：
Y. Guéguen
中科院分区：
文献类型：
--
作者：
M. Darot;Y. Guéguen
镁橄榄石单晶的蠕变已根据差异应力的方向进行了研究。研究了三个方向：[110]c、[101]c 和[011]c。在室温和受控气氛下，在恒载蠕变装置中，样品在高温 (T ≥ 1400°C) 和中等应力 (15 < σ < 110 MPa) 下变形。假设蠕变定律的一般形式为 = Aσn exp −(Q/RT)，进行了两个不同的测试。应力阶跃和温度阶跃实验分别给出了应力指数n和活化能Q。使用光学显微镜（装饰薄片）和透射电子显微镜对潜在滑移面中的位错微观结构进行了彻底分析。通过比较机械和微观结构数据，可以确定所研究的三个方向的不同流动规律。镁橄榄石和橄榄石数据一致；流动定律和位错微观结构相似。根据这些结果，将流动定律外推到地幔的应力条件并不简单。低应力 (σ < 15 MPa) 下的非常高的活化能可能表明流动机制发生了变化。因此，需要在低应力领域进行进一步的研究。
Creep of forsterite single crystals has been studied with respect to the orientation of the differential stress. Three orientations have been investigated: [110]c, [101]c, and [011]c. Specimens were deformed at high temperature (T ≥ 1400°C) and moderate stresses (15 < σ < 110 MPa) in a dead load creep apparatus at room pressure and under controlled atmosphere. Assuming that the creep law has the general form = Aσn exp −(Q/RT), two different tests were performed. Stress step and temperature step experiments gave the stress exponent n and the activation energy Q, respectively. A thorough analysis of the dislocation microstructures was carried out in the potential glide planes using the optical microscope (decorated thin section) and transmission electron microscope. Comparison of both mechanical and microstructural data allowed the determination of the different flow laws for the three orientations studied. Forsterite and olivine data are consistent; both flow laws and dislocation microstructures are similar. In light of these results, extrapolation of flow laws to the stress conditions of the mantle is not straightforward. Very high activation energies at low stresses (σ < 15 MPa) may suggest a change of flow mechanisms. Accordingly, further investigations in the low-stress domain are required.