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In-situ 3DXRD annealing of a geological material: Evaluating the validity of 2D 
Stockholm University, Faculty of Science, Department of Geological Sciences. (Petrotectonics)
Materials Research Division, Risø DTU.
Stockholm University, Faculty of Science, Department of Geological Sciences. (Petrotectonics)
MaxLab, Lund University.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Most in-situ heating experiments where substructure is investigated have been restricted to 2D. We compare a 2D experiment to a 3D X-ray diffraction experiment to evaluate the validity of the 2D method. Until now 3D X-ray diffraction has been limited to well-recovered substructures. We conducted a 3D in-situ annealing experiment on a halite crystal with a significant orientation gradient. This is the first experiment of its kind on a geological material and shows that even complicated microstructures can be resolved. Comparison of 2D and 3D showed that, although general results were similar, subgrain boundary movement occurred with higher frequency in 3D. We suggest this discrepancy is due to enhanced drag force on subgrain boundaries by surface thermal grooving. Thus, while results from 2D experiments largely reflect what is happening in the volume, analysis of boundary movement with regard to absolute mobilities needs to be considered with some care.

Research subject
URN: urn:nbn:se:su:diva-45685OAI: diva2:369337
Available from: 2010-11-10 Created: 2010-11-10 Last updated: 2010-11-30Bibliographically approved
In thesis
1. Fundamentals of substructure dynamics: In-situ experiments and numerical simulation
Open this publication in new window or tab >>Fundamentals of substructure dynamics: In-situ experiments and numerical simulation
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Substructure dynamics incorporate all features occurring on a subgrain-scale. The substructure governs the rheology of a rock, which in turn determines how it will respond to different processes during tectonic changes. This project details an in-depth study of substructural dynamics during post-deformational annealing, using single-crystal halite as an analogue for silicate materials. The study combines three different techniques; in-situ annealing experiments conducted inside the scanning electron microscope and coupled with electron backscatter diffraction, 3D X-ray diffraction coupled with in-situ heating conducted at the European Radiation Synchrotron Facility and numerical simulation using the microstructural modelling platform Elle. The main outcome of the project is a significantly refined model for recovery at annealing temperatures below that of deformation preceding annealing. Behaviour is highly dependent on the temperature of annealing, particularly related to the activation temperature of climb and is also strongly reliant on short versus long range dislocation effects. Subgrain boundaries were categorised with regard to their behaviour during annealing, orientation and morphology and it was found that different types of boundaries have different behaviour and must be treated as such. Numerical simulation of the recovery process supported these findings, with much of the subgrain boundary behaviour reproduced with small variation to the mobilities on different rotation axes and increase of the size of the calculation area to imitate long-range dislocation effects. Dislocations were found to remain independent to much higher misorientation angles than previously thought, with simulation results indicating that change in boundary response occurs at ~7º for halite. Comparison of 2D experiments to 3D indicated that general boundary behaviour was similar within the volume and was not significantly influenced by effects from the free surface. Boundary migration, however, occurred more extensively in the 3D experiment. This difference is interpreted to be related to boundary drag on thermal grooves on the 2D experimental surface. While relative boundary mobilities will be similar, absolute values must therefore be treated with some care when using a 2D analysis.

Place, publisher, year, edition, pages
Stockholm: Department of Geological Sciences, Stockholm University, 2010. 23 p.
Meddelanden från Stockholms universitets institution för geologiska vetenskaper, 342
halite, in-situ, X-ray diffraction, EBSD, annealing, substructure, modelling
National Category
Earth and Related Environmental Sciences
Research subject
urn:nbn:se:su:diva-45811 (URN)978-91-7447-187-8 (ISBN)
Public defence
2010-12-20, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:30 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.Available from: 2010-11-28 Created: 2010-11-11 Last updated: 2010-12-03Bibliographically approved

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