Preferred Orientation of Quartz in Metamorphic Rocks from the Bergell Alps

Crystal preferred orientation of 47 samples of quartzite and eight samples of associated marbles from the Bergell Alps have been analyzed with time-of-flight neutron diffraction and EBSD. The results show a clear distinction of texture types for quartzites transformed from Triassic sandstones and quartz layers in gneiss. Textures of Triassic quartzites are overall weak and display a maximum of c-axes perpendicular to the foliation or a crossed girdle perpendicular to the lineation. Pole figures for positive rhombs {10 1 ¯ 1} show a maximum perpendicular to the foliation and negative rhombs {01 1 ¯ 1} generally display a minimum. Based on polycrystal plasticity models this texture type can be attributed to a combination of basal and rhombohedral slip. Asymmetry of the distributions is attributed to simple shear and local strain heterogeneities. The relatively weak texture is partially caused by muscovite limiting dislocation motion and grain growth, as well as adjacent layers of marble that accommodate significant strain. Most quartz layers in gneiss, including mylonites, display a texture with a-axes parallel to the lineation and a c-axis maximum in the intermediate fabric direction. This texture type can be attributed to dominant prismatic slip. Many samples are recrystallized and recrystallization appears to strengthen the deformation texture. The study shows good agreement of neutron diffraction and EBSD. Neutron diffraction data average over larger volumes and maximum pole densities are generally lower and more representative for the bulk material. With EBSD the microstructure and mechanical twinning can be quantified.

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Quantitative texture analysis by neutron diffraction in deformed crystalline aggregates: Contín Shear Zone, Morais Complex, N Portugal.

10.5194/egusphere-egu2020-6714 ◽

2020 ◽

Author(s):

Manuela Durán Oreja ◽

Jeremie Malecki ◽

Juan Gómez Barreiro

Keyword(s):

Neutron Diffraction ◽

Shear Zone ◽

Seismic Anisotropy ◽

Preferred Orientation ◽

Distribution Functions ◽

P Wave ◽

Orientation Data ◽

Crystal Preferred Orientation ◽

Two Samples

<p>Two samples of mylonitic-ultramylonitic ortogneisses collected along the Cont&#237;n shear zone were investigated for crystal preferred orientation and seismic anisotropy. Neutron diffraction data obtained at the D1B beamline at ILL (Institute Laue-Langevin, Grenoble) were analyzed with the Rietveld method as implemented in the code MAUD, to obtain the orientation distribution functions (ODF) of the principal phases (quartz, K-feldspar, plagioclase, phlogopite, muscovite and riebeckite). Texture and microstructure are compatible with the plastic deformation of the aggregates under medium to low-temperature conditions. Kinematic analysis supports a top-to-the SE sense of shear, suggesting a thrust character. Using preferred orientation data and single crystal elastic tensors, P and S-waves velocities and elastic anisotropy have been calculated. We have explored the role of several factors controlling the elastic properties of rocks, particularly the role of strain state and mineral changes in a shear zone. Those factors have a direct impact on the medium impedance and consequently on the interphase reflectivity. P-wave velocities, S-wave splitting and anisotropy increase with muscovite content. Seismic anisotropy is linked with the texture symmetry, which can result in large deviations between actual anisotropy and that measured along Cartesian XYZ sample directions (lineation/foliation reference frame). This is significant for the prediction and interpretation of seismic data. (Research support CGL2016-78560-P)</p>

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Kinetics of cyclically-induced mechanical twinning in γ-TiAl unveiled by a combination of acoustic emission, neutron diffraction and electron microscopy

Acta Materialia ◽

10.1016/j.actamat.2021.116921 ◽

2021 ◽

pp. 116921

Author(s):

A. Vinogradov ◽

M. Heczko ◽

V. Mazánová ◽

M. Linderov ◽

T. Kruml

Keyword(s):

Electron Microscopy ◽

Acoustic Emission ◽

Neutron Diffraction ◽

Mechanical Twinning ◽

Kinetics Of

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Rietveld texture analysis from TOF neutron diffraction data

Powder Diffraction ◽

10.1154/1.3479004 ◽

2010 ◽

Vol 25 (3) ◽

pp. 283-296 ◽

Cited By ~ 118

Author(s):

H.-R. Wenk ◽

L. Lutterotti ◽

S. C. Vogel

Keyword(s):

Neutron Diffraction ◽

Texture Analysis ◽

Electron Backscatter Diffraction ◽

Computer Code ◽

Preferred Orientation ◽

Complex Data ◽

Ambient Conditions ◽

Science Center ◽

Step Procedure ◽

Backscatter Diffraction

One of the advantages of a multidetector neutron time-of-flight diffractometer such as the high pressure preferred orientation diffractometer (HIPPO) at the Los Alamos Neutron Science Center is the capability to measure efficiently preferred orientation of bulk materials. A routine experimental method for measurements, both at ambient conditions, as well as high or low temperatures, has been established. However, only recently has the complex data analysis been streamlined to make it straightforward for a noninitiated user. Here, we describe the Rietveld texture analysis of HIPPO data with the computer code Materials Analysis Using Diffraction (MAUD) as a step-by-step procedure and illustrate it with a metamorphic quartz rock. Postprocessing of the results is described and neutron diffraction results are compared with electron backscatter diffraction measurements on the same sample.

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Using electron backscatter diffraction to measure full crystallographic orientation in Antarctic land-fast sea ice

Journal of Glaciology ◽

10.1017/jog.2018.67 ◽

2018 ◽

Vol 64 (247) ◽

pp. 771-780 ◽

Cited By ~ 3

Author(s):

PAT WONGPAN ◽

DAVID J. PRIOR ◽

PATRICIA J. LANGHORNE ◽

KATHERINE LILLY ◽

INGA J. SMITH

Keyword(s):

Sea Ice ◽

Crystallographic Orientation ◽

Electron Backscatter Diffraction ◽

Preferred Orientation ◽

Angle Distribution ◽

Crystal Preferred Orientation ◽

Electron Backscatter ◽

Backscatter Diffraction ◽

First Time ◽

Platelet Ice

ABSTRACTWe have mapped the full crystallographic orientation of sea ice using electron backscatter diffraction (EBSD). This is the first time EBSD has been used to study sea ice. Platelet ice is a feature of sea ice near ice shelves. Ice crystals accumulate as an unconsolidated sub-ice platelet layer beneath the columnar ice (CI), where they are subsumed by the advancing sea–ice interface to form incorporated platelet ice (PI). As is well known, in CI the crystal preferred orientation comprises dominantly horizontal c-axes, while PI has c-axes varying between horizontal and vertical. For the first time, this study shows the a-axes of CI and PI are not random. Misorientation analysis has been used to illuminate the possible drivers of these alignments. In CI the misorientation angle distribution from random pairs and neighbour pairs of grains are indistinguishable, indicating the distributions are a consequence of crystal preferred orientation. Geometric selection during growth will develop the a-axis alignment in CI if ice growth in water is fastest parallel to the a-axis, as has previously been hypothesised. In contrast, in PI random-pair and neighbour-pair misorientation distributions are significantly different, suggesting mechanical rotation of crystals at grain boundaries as the most likely explanation.

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Correlating work hardening with co-activation of stacking fault strengthening and transformation in a high entropy alloy using in-situ neutron diffraction

Scientific Reports ◽

10.1038/s41598-020-79492-8 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

M. Frank ◽

S. S. Nene ◽

Y. Chen ◽

B. Gwalani ◽

E. J. Kautz ◽

...

Keyword(s):

Neutron Diffraction ◽

Work Hardening ◽

Dislocation Motion ◽

Stacking Fault ◽

Dislocation Slip ◽

Simultaneous Increase ◽

High Entropy Alloy ◽

High Entropy ◽

In Situ Neutron Diffraction

AbstractTransformation induced plasticity (TRIP) leads to enhancements in ductility in low stacking fault energy (SFE) alloys, however to achieve an unconventional increase in strength simultaneously, there must be barriers to dislocation motion. While stacking faults (SFs) contribute to strengthening by impeding dislocation motion, the contribution of SF strengthening to work hardening during deformation is not well understood; as compared to dislocation slip, twinning induced plasticity (TWIP) and TRIP. Thus, we used in-situ neutron diffraction to correlate SF strengthening to work hardening behavior in a low SFE Fe40Mn20Cr15Co20Si5 (at%) high entropy alloy, SFE ~ 6.31 mJ m−2. Cooperative activation of multiple mechanisms was indicated by increases in SF strengthening and γ-f.c.c. → ε-h.c.p. transformation leading to a simultaneous increase in strength and ductility. The present study demonstrates the application of in-situ, neutron or X-ray, diffraction techniques to correlating SF strengthening to work hardening.

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