The influence of strain rate and presence of dispersed second phases on the deformation behaviour of polycrystalline D₂O ice

Abstract

This contribution discusses results obtained from 3-D neutron diffraction and 2-D fabric analyser in situ deformation experiments on laboratory-prepared polycrystalline deuterated ice and ice containing a second phase. The two-phase samples used in the experiments are composed of an ice matrix with (1) air bubbles, (2) rigid, rhombohedral-shaped calcite and (3) rheologically soft, platy graphite. Samples were tested at 10°C below the melting point of deuterated ice at ambient pressures, and two strain rates of 1 × 10−5 s−1 (fast) and 2.5 × 10−6 s−1 (medium). Nature and distribution of the second phase controlled the rheological behaviour of the ice by pinning grain boundary migration. Peak stresses increased with the presence of second-phase particles and during fast strain rate cycles. Ice-only samples exhibit well-developed crystallographic preferred orientations (CPOs) and dynamically recrystallized microstructures, typifying deformation via dislocation creep, where the CPO intensity is influenced in part by the strain rate. CPOs are accompanied by a concentration of [c]-axes in cones about the compression axis, coinciding with increasing activity of prismatic-<a> slip activity. Ice with second phases, deformed in a relatively slower strain rate regime, exhibit greater grain boundary migration and stronger CPO intensities than samples deformed at higher strain rates or strain rate cycles.

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

“…To our knowledge, Fig. 14 and Russell-Head, 1982;Gao and Jacka, 1987;Treverrow et al, 2012;Wilson et al, 2019). These data are consistent with the pattern shown in Fig.…”

“…For data from the literature, we digitised the c-axis orientations from published stereonets (Jacka and Maccagnan, 1984;Jacka and Li, 2000) and calculated using the same method described in Section two (Method). For data Piazolo and others (2013) were conducted on D2O ice at -7 °C, which is a direct analogue for deforming H2O ice at −10 °C (Wilson et al, 2019). These angles were analysed using methods similar to ours.…”

“…The data from constant displacement rate experiments on D2O ice (Piazolo et al, 2013) are illustrated by hollow circles. The deformation of D2O ice at -7 °C is a direct analogue for deforming H2O ice at −10 °C (Wilson et al, 2019). The data from constant displacement rate experiments on H2O ice (this study, Vaughan et al, 2017, Qi et al, 2017, Craw et al, 2018 are illustrated by filled circles.…”

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

“…There are numerous other high-temperature and low-strain-rate axial compression experiments to strains of ∼ 10 % to 30 % where c-axis cones have opening angles of ∼ 35 • (e.g. Wilson and Russell-Head, 1982;Gao and Jacka, 1987;Treverrow et al, 2012;Wilson et al, 2019). These data are consistent with the pattern shown in Fig.…”

“…Wilson et al (2020) are taken directly from these papers. The experiments reported by Piazolo et al (2013) were conducted on D 2 O ice at −7 • C, which is a direct analogue for deforming H 2 O ice at −10 • C (Wilson et al, 2019). These angles were analysed using methods similar to ours.…”