Water assisted dynamic recrystallization and weakening in polycrystalline bischofite
Water assisted dynamic recrystallization and weakening in polycrystalline bischofite
复制标题
水辅助动态重结晶和多晶水氯镁石的弱化
DOI：
10.1016/0040-1951(83)90247-0
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发表时间：
1983
期刊：
影响因子：
2.9
通讯作者：
J. Urai
中科院分区：
文献类型：
--
作者：
J. Urai
在温度20℃~100℃，应变速率10−4~10−88s−1，围压0.1~28 Mpa的条件下，对人工制备的水氯镁石(氯化镁-6H2O)进行了实验变形。通过原位变形实验研究了变形过程中显微组织随应变的变化规律，并与变形样品的薄片观察结果进行了关联。在第一系列实验中，研究了晶粒度、杂质含量和水分含量对流动行为的影响。在干燥样品中加入约0.1wt.%的水可使流动应力降低5倍，这可能与在晶界上形成一层薄的流体膜，由于大角度晶界的移动而强烈促进动态再结晶有关，也可能是由于晶格中存在过多的水而提高了晶内塑性。在第二系列实验中，研究了选定样品的流动应力的应变率敏感性。结果表明，当应力差值大于2.0 Mpa时，蠕变方程中的应力指数n=4.5，小于2.0 Mpa时，应力指数n=1.5，变形机制主要为晶内滑移、孪生和晶界滑移。再结晶是通过亚晶旋转和大角度晶界迁移进行的。晶界迁移率分为两种不同的制度，一种制度是以极快的迁移率来区分的。讨论了实验发现的流动规律对水氯镁石岩在自然界中行为的适用性。
Artificially prepared specimens of bischofite (MgCl2-6H2O) have been experimentally deformed at temperatures between 20 and 100°C, strain rates between 10−4and 10−88s−1, and confining pressures between 0.1 and 28 MPa. Development of microstructure with strain was studied by in-situ deformation experiments, and results of these were correlated with observations made on thin sections of deformed samples.In a first series of experiments the effect of grain size, impurity content and water content on the flow behaviour was investigated. Addition of about 0.1 wt.% water to dry samples was found to decrease the flow stress by a factor of 5. This effect was found to be associated with the formation of a thin fluid film on grain boundaries, strongly enhancing dynamic recrystallization due to the movement of high-angle grain boundaries, and possibly also to enhanced intracrystalline plasticity due to excess water present in the lattice. In a second series of experiments the strain-rate sensitivity of the flow stress of selected samples was investigated. Two regimes could be distinguished: one with a stress exponentn= 4.5 in the power law creep equation for values of the differential stress above 2.0 MPa, and one withn= 1.5 for stresses below this value.The main deformation mechanisms were intracrystalline slip, twinning, and grain-boundary sliding. Recrystallization occurred by subgrain rotation and high-angle grain-boundary migration. The rates of grain-boundary migration fell into two different regimes, one regime being distinguished by extremely fast migration rates. The applicability of the experimentally found flow law to the behaviour of bischofite rocks in nature is discussed.