Ultramylonite generation via phase mixing in high‐strain experiments
Ultramylonite generation via phase mixing in high‐strain experiments
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高应变实验中通过相混合生成超糜棱岩
DOI：
10.1002/2016jb013801
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
P. Skemer
中科院分区：
文献类型：
--
作者：
A. Cross;P. Skemer
动态再结晶和相混合被认为是韧性剪切带形成的重要过程，因为它们共同使其永久过渡到应变弱化、晶粒尺寸敏感的变形状态。虽然动态再结晶已被很好地理解，但相混合所需的基本物理过程和时间尺度仍然是谜。本文介绍了方解石-硬石膏复合材料的高应变相混合实验结果。以细粒方解石和硬石膏粉为原料，合成了一种混合不良的原料。样品在500℃的大体积扭转装置中变形，剪切应变率为5 × 10−5至5 × 10−4 s−1，有限剪切应变高达γ = 57。通过分析后向散射电子图像和电子后向散射衍射数据，量化了微观结构的演变。在变形过程中，单个相的多晶畴被几何拉伸和变薄，导致相间边界的空间密度增加。在中等剪切应变（γ≥6）下，畴严重变薄，成为只有一到两个晶粒宽度的“单层”，形成薄的成分层。单分子层的形成伴随着晶界固定程度的临界增加，因此，晶粒尺寸减小到由晶粒尺寸计或变形机制确定的理论极限以下。最终，单分子膜在高应变下收缩并分解（17）
Dynamic recrystallization and phase mixing are considered to be important processes in ductile shear zone formation, as they collectively enable a permanent transition to the strain‐weakening, grain‐size sensitive deformation regime. While dynamic recrystallization is well understood, the underlying physical processes and timescales required for phase mixing remain enigmatic. Here, we present results from high‐strain phase mixing experiments on calcite‐anhydrite composites. A poorly mixed starting material was synthesized from fine‐grained calcite and anhydrite powders. Samples were deformed in the Large Volume Torsion apparatus at 500°C and shear strain rates of 5 × 10−5 to 5 × 10−4 s−1, to finite shear strains of up to γ = 57. Microstructural evolution is quantified through analysis of backscattered electron images and electron backscatter diffraction data. During deformation, polycrystalline domains of the individual phases are geometrically stretched and thinned, causing an increase in the spatial density of interphase boundaries. At moderate shear strains (γ ≥ 6), domains are so severely thinned that they become “monolayers” of only one or two grain's width and form a thin compositional layering. Monolayer formation is accompanied by a critical increase in the degree of grain boundary pinning and, consequently, grain‐size reduction below the theoretical limit established by the grain‐size piezometer or deformation mechanism field boundary. Ultimately, monolayers neck and disaggregate at high strains (17
通过 EBSD 分析表征自然变形细粒硬石膏的微观结构并解释流动机制
DOI：
10.1144/sp360.14
发表时间：
2022
期刊：
Geological Society, London, Special Publications
影响因子：
--
作者：
Hildyard R
通讯作者：
Hildyard R