The role of kink boundaries in the deformation and recrystallisation of polycrystalline ice

Seidemann, M.; Prior, David J.; Golding, N.; Durham, W. B.; Lilly, Kat; Vaughan, M. J.

doi:10.1016/j.jsg.2020.104010

Cited by 10 publications

(15 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The subgrain boundaries and the pattern of misorientation angles are commonly interpreted as the result of dynamic recovery of dislocations generated during deformation and subsequent subgrain rotation related to ongoing recovery (Guillope and Poirier, 1979;Trimby et al, 1998;Fliervoet et al, 1999;Wheeler et al, 2001) and has been observed from ice deformation experiments previously and interpreted in this way (e.g. Montagnat et al, 2015;Qi et al, 2017;Seidemann at al., 2020). The misorientation angle at which neighbour-pair frequency has reduced to be equal to the random-pair frequency increases with decreasing temperature (Figs.…”

Section: Dislocation Activity Recovery Subgrain Rotation and Subgramentioning

confidence: 91%

“…quartz (Cross et al, 2017a;Kilian and Heilbronner, 2017), olivine (Hansen et al, 2012), Magnox alloy (Wheeler et al, 2009) and zircon (MacDonald et al, 2013). The misorientation axes for subgrain boundaries are generally rotations around rational crystallographic axes, particularly directions in the basal plane, suggesting that the boundaries may represent arrays of dislocations (Humphreys and Hatherley, 2004;Shigematsu et al, 2006). There is much higher frequency of low-angle (Particularly < 10 • ) neighbour-pair misorientations than is expected from the CPO (as shown by the random-pair misorientation angles).…”

Section: Dislocation Activity Recovery Subgrain Rotation and Subgramentioning

confidence: 99%

See 1 more Smart Citation

Temperature and strain controls on ice deformation mechanisms: insights from the microstructures of samples deformed to progressively higher strains at −10, −20 and −30 °C

et al. 2020

Self Cite

View full text Add to dashboard Cite

Abstract. In order to better understand ice deformation mechanisms, we document the microstructural evolution of ice with increasing strain. We include data from experiments at relatively low temperatures (−20 and −30 ∘C), where the microstructural evolution with axial strain has never before been documented. Polycrystalline pure water ice was deformed under a constant displacement rate (strain rate ∼1.0×10-5 s−1) to progressively higher strains (∼ 3 %, 5 %, 8 %, 12 % and 20 %) at temperatures of −10, −20 and −30 ∘C. Microstructural data were generated from cryogenic electron backscattered diffraction (cryo-EBSD) analyses. All deformed samples contain subgrain (low-angle misorientations) structures with misorientation axes that lie dominantly in the basal plane, suggesting the activity of dislocation creep (glide primarily on the basal plane), recovery and subgrain rotation. Grain boundaries are lobate in all experiments, suggesting the operation of strain-induced grain boundary migration (GBM). Deformed ice samples are characterized by interlocking big and small grains and are, on average, finer grained than undeformed samples. Misorientation analyses between nearby grains in 2-D EBSD maps are consistent with some 2-D grains being different limbs of the same irregular grain in the 3-D volume. The proportion of repeated (i.e. interconnected) grains is greater in the higher-temperature experiments suggesting that grains have more irregular shapes, probably because GBM is more widespread at higher temperatures. The number of grains per unit area (accounting for multiple occurrences of the same 3-D grain) is higher in deformed samples than undeformed samples, and it increases with strain, suggesting that nucleation is involved in recrystallization. “Core-and-mantle” structures (rings of small grains surrounding big grains) occur in −20 and −30 ∘C experiments, suggesting that subgrain rotation recrystallization is active. At temperatures warmer than −20 ∘C, c axes develop a crystallographic preferred orientation (CPO) characterized by a cone (i.e. small circle) around the compression axis. We suggest the c-axis cone forms via the selective growth of grains in easy slip orientations (i.e. ∼ 45∘ to shortening direction) by GBM. The opening angle of the c-axis cone decreases with strain, suggesting strain-induced GBM is balanced by grain rotation. Furthermore, the opening angle of the c-axis cone decreases with temperature. At −30 ∘C, the c-axis CPO changes from a narrow cone to a cluster, parallel to compression, with increasing strain. This closure of the c-axis cone is interpreted as the result of a more active grain rotation together with a less effective GBM. We suggest that lattice rotation, facilitated by intracrystalline dislocation glide on the basal plane, is the dominant mechanism controlling grain rotation. Low-angle neighbour-pair misorientations, relating to subgrain boundaries, are more extensive and extend to higher misorientation angles at lower temperatures and higher strains supporting a relative increase in the importance of dislocation activity. As the temperature decreases, the overall CPO intensity decreases, primarily because the CPO of small grains is weaker. High-angle grain boundaries between small grains have misorientation axes that have distributed crystallographic orientations. This implies that, in contrast to subgrain boundaries, grain boundary misorientation is not controlled by crystallography. Nucleation during recrystallization cannot be explained by subgrain rotation recrystallization alone. Grain boundary sliding of finer grains or a different nucleation mechanism that generates grains with random orientations could explain the weaker CPO of the fine-grained fraction and the lack of crystallographic control on high-angle grain boundaries.

show abstract

Section: Dislocation Activity Recovery Subgrain Rotation and Subgramentioning

confidence: 91%

Section: Dislocation Activity Recovery Subgrain Rotation and Subgramentioning

confidence: 99%

Temperature and strain controls on ice deformation mechanisms: insights from the microstructures of samples deformed to progressively higher strains at −10, −20 and −30 °C

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…The rotation axes of the analyzed samples, shown in Figure 8, can be classified into two types: one parallel to the c-axes that is activated at the depths of 50, 140, and 170 m, and another along the basal plane that has been highlighted at all depths except at 140 m. Assuming that only the basal slip system is active, rotation axes parallel to the c-axis can be related to twist walls (screw dislocations) of the basal slip system, while rotation axes along the basal plane can be related to tilt walls (edge dislocations) of the basal slip system. Statistically significant data sets from experiments identify both of these rotation axes [26,71] and subgrain boundary trace analyses, and weighted burgers vector analyses [72] of these same samples (Sheng Fan, personal communication) indicate that the rotation axes in basal plane are clearly related to basal plane dislocations. Other studies have constrained the operation of non-basal dislocations in both experimental [73,74] and natural [70,75] ice and further work is needed to determine the contribution of non-basal dislocations in these samples.…”

Section: Recrystallization Processes and Slip Systemsmentioning

confidence: 98%

Microstructures and Fabric Transitions of Natural Ice from the Styx Glacier, Northern Victoria Land, Antarctica

et al. 2020

Self Cite

View full text Add to dashboard Cite

We investigated the microstructures of five ice core samples from the Styx Glacier, northern Victoria Land, Antarctica. Evidence of dynamic recrystallization was found in all samples: those at 50 m mainly by polygonization, and those at 170 m, largely by grain boundary migration. Crystallographic preferred orientations of all analyzed samples (view from the surface) typically showed a single cluster of c-axes normal to the surface. A girdle intersecting the single cluster occurs at 140–170 m with a tight cluster of a-axes normal to the girdle. We interpret the change of crystallographic preferred orientations (CPOs) at <140 m as relating to a combination of vertical compression, and shear on a horizontal plane, and the girdle CPOs at depths >140 m, as the result of horizontal extension. Based on the data obtained from the ground penetrating radar, the underlying bedrock topography of a nunatak could have generated the extensional stress regime in the study area. The results imply changeable stress regimes that may occur during burial as a result of external kinematic controls, such as an appearance of a small peak in the bedrock.

show abstract

“…Lamellae of clinopyroxene are common in orthopyroxene grains in harzburgites (Figure 4a) and lherzolites (Figure 4f). Bent clinopyroxene lamellae, corresponding to straight subgrain boundaries in the orthopyroxene, form a kink band-like geometry (the inset of Figures 4f and S1; Seidemann et al, 2020). Lamellae near subgrain boundaries are slightly thicker, branching of the subgrain boundary occurs close to the intersection with lamellae, and the bend in the clinopyroxene occurs across one or more subgrain boundaries (inset of Figure 4f).…”

Section: Microstructuresmentioning

confidence: 99%

Pre‐Alpine Fault Fabrics in Mantle Xenoliths From East Otago, South Island, New Zealand

et al. 2020

Self Cite

View full text Add to dashboard Cite

In the last century geophysicists discovered that seismic velocity in the Earth's upper mantle is anisotropic and inferred that the crystallographic preferred orientations (CPOs) of olivine in the subcontinental lithospheric mantle (SCLM) contributes significantly to this anisotropy (Hess, 1964; Nicolas & Christensen, 1987). During the last two decades, measurements of the CPOs of natural samples (orogenic mantle slices and mantle xenoliths) and the products of laboratory experiments have established a framework of olivine CPO types and understanding of how these CPOs relate to deformation processes and how they contribute to seismic anisotropy (

show abstract

The role of kink boundaries in the deformation and recrystallisation of polycrystalline ice

Cited by 10 publications

References 45 publications

Temperature and strain controls on ice deformation mechanisms: insights from the microstructures of samples deformed to progressively higher strains at −10, −20 and −30 °C

Temperature and strain controls on ice deformation mechanisms: insights from the microstructures of samples deformed to progressively higher strains at −10, −20 and −30 °C

Microstructures and Fabric Transitions of Natural Ice from the Styx Glacier, Northern Victoria Land, Antarctica

Pre‐Alpine Fault Fabrics in Mantle Xenoliths From East Otago, South Island, New Zealand

Contact Info

Product

Resources

About