Development of microstructure during deformation of carnallite and bischofite in transmitted light

Urai, János L.

doi:10.1016/0040-1951(87)90166-1

Cited by 58 publications

(29 citation statements)

References 12 publications

(22 reference statements)

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“…In particular, grain dissection is most effective during the second stage of the high strain-rate simulations ( Figure 6C). The observation of efficient grain dissection at steady-state conditions is consistent with experimental results by Jessell (1986) and Urai (1987). When the mean grain size is larger than the equilibrium one and thus grain size decreases, polygonisation dominates over dissection, as is observed in the high strain-rate simulations and in rock analog experiments by Herwegh et al (1997).…”

Section: Time-resolved Numerical Microstructure Evolution Under the Isupporting

confidence: 88%

“…All simulations show situations that can be identified as grain dissection in the sense of the descriptions by Urai (1987) and Means (1983,1989) (see movies, Supplementary Material). The simulations provide a time series to study the interaction of this process with polygonisation, recovery, grain boundary migration and viscoplastic deformation and their relative contribution to microstructure evolution.…”

Section: Time-resolved Numerical Microstructure Evolution Under the Imentioning

confidence: 91%

“…Resulting groups of grains with similar orientation were called "orientation families" by Urai (1983). This process was termed grain dissection by Urai et al (1986) and Urai (1987) is known as geometric dynamic recrystallization in metallurgy (Humphreys and Hatherly, 2004, pp. 461-465;De Meer et al, 2002; Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…So far, it is assumed that stable grain sizes in ice are achieved by an interplay of dynamic graingrowth, polygonisation and potentially nucleation processes (Alley et al, 1995;De La Chapelle et al, 1998;Montagnat and Duval, 2000;Mathiesen et al, 2004;Roessiger et al, 2011;Chauve et al, 2017;Hidas et al, 2017). However, in rock analogs and bischofite, grain dissection is observed as an effective grain-sizereducing process, in particular at steady-state grain sizes (Jessell, 1986;Urai, 1987).…”

Section: Introductionmentioning

confidence: 99%

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The Relevance of Grain Dissection for Grain Size Reduction in Polar Ice: Insights from Numerical Models and Ice Core Microstructure Analysis

et al. 2017

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The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modeling and analyzed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM) project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD) have been used together with c-axis orientations using an optical technique (Fabric Analyser). Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighboring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modeling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be used to identify grain dissection in natural microstructures.

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Section: Time-resolved Numerical Microstructure Evolution Under the Isupporting

confidence: 88%

Section: Time-resolved Numerical Microstructure Evolution Under the Imentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Relevance of Grain Dissection for Grain Size Reduction in Polar Ice: Insights from Numerical Models and Ice Core Microstructure Analysis

et al. 2017

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“…However, so far it has been poorly understood. In previous studies the fluid distribution has been investigated through microstructures of deformed materials [e.g., Urai et al, 1986a] or ''see-through'' experiments [e.g., Urai, 1987]. Although the structure of fluid phase is mostly preserved after deformation, the fine structure is likely to be modified rapidly.…”

Section: Introductionmentioning

confidence: 99%

Electrical impedance measurement of plastically deforming halite rocks at 125°C and 50 MPa

Watanabe

Peach

2002

J. Geophys. Res.

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[1 ] Electrical impeda nce meas urements have been perfor med on deform ing fine-grai ned ( $ 300 m m) synth etic halite rocks contain ing small quan tities of water in order to study the evo lution of fluid distribution. Experiments were carried out on four wet samples (H 2 O~30 ppm) and one ''dry'' sample (H 2 O~5 ppm) under nondilatant condition (125°C, 50 MPa confining pressure, and strain rate of $5 Â 10 À7 s À1 ), using a triaxial deformation apparatus. The mechanical behavior of wet and dry samples is strikingly different. Only $30 ppm water greatly weakens halite rocks through grain boundary migration recrystallization. Wet experiments show oscillating stress-strain curves, reflecting the competition between work hardening and weakening due to dynamic recrystallization. The dry experiment shows neither weakening nor recrystallized microstructure. The measured impedance shows that an interconnected network of water is formed even in the dry sample and that the connectivity in bulk is attained through the very thin (1 -10 nm) elements of fluid. The resistivity change with deformation suggests the competition between thinning and thickening of connected fluid paths. The thinning is caused by fluid squirt due to the axial compression, and the thickening is caused by fluid squirt due to the grain growth due to fluidassisted grain boundary migration. In wet samples the diffusivity through grain boundary water is estimated to be lower than the bulk water by 5-6 orders of magnitude. In the dry sample, grain boundary water is thinner, and its diffusivity might not be high enough to promote grain boundary migration. Observed migration recrystallization can occur in natural conditions and greatly weaken salt rocks. The impedance measurement is very useful to track the evolution of fluid distribution in deforming materials. For further understanding of mechanical and electrical properties of halite rocks it is essential to clarify properties of thin water films.INDEX TERMS: 5104 Physical Propert ies of Rocks: Fractu re and flow, 5112 Physic al Propert ies of Roc ks: Micr ostructur e, 5120

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Microscopy of Rocks and Minerals

Amelinckx¹,

Dyck²,

Landuyt³

et al. 1996

Handbook of Microscopy Set

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Development of microstructure during deformation of carnallite and bischofite in transmitted light

Cited by 58 publications

References 12 publications

The Relevance of Grain Dissection for Grain Size Reduction in Polar Ice: Insights from Numerical Models and Ice Core Microstructure Analysis

The Relevance of Grain Dissection for Grain Size Reduction in Polar Ice: Insights from Numerical Models and Ice Core Microstructure Analysis

Electrical impedance measurement of plastically deforming halite rocks at 125°C and 50 MPa

Microscopy of Rocks and Minerals

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