Abstract
ABSTRACTWe investigated the effects of microparticles and grain size on the microstructural evolutions and mechanical properties of polycrystalline ice. Uniaxial compression tests were conducted using fine-grained pure ice and silica-dispersed ice under various conditions. Deformation behavior of fine-grained ice was found to be characterized by stress exponent n ≈ 2 and activation energy Q ≈ 60 kJ mol−1. The derived strain rates of fine-grained ice were ≈ 1 order of magnitude larger than those of coarse-grained ice obtained in previous studies, and they were found to be independent of particle dispersion and dependent on the mean grain size of ice, with grain size exponent p ≈ 1.4. Work hardening was observed in dislocation creep, while the strain rate continued to decrease. These results indicate that the deformation mechanism of fine-grained ice is different from typical dislocation creep, often associated with n = 3. Although microparticles restricted grain growth, there was little direct effect on the deformation of fine-grained ice. Microstructural observations of the ice samples indicated that the grain boundaries were straight and that the subgrain boundary densities increased after deformation. Our experiments suggest that grain size and boundaries play important roles in the deformation processes of polycrystalline ice.
Highlights
The behaviors of the Greenland and Antarctic ice sheets play fundamental roles in global climate change
This study investigated the influences of microparticles, grain size and grain boundaries (GBs) on polycrystalline ice deformation via laboratory-based deformation experiments and microstructural observations
Based on the findings of the deformation experiments and microstructural observations, we discuss the effects of microparticles and GBs on the deformation of ice-sheet ice, and we propose a possible reason for the observed rapid deformation of ice-age ice
Summary
The behaviors of the Greenland and Antarctic ice sheets play fundamental roles in global climate change. It was argued that the hardening of ice is similar to the dispersion hardening of metals, and that the sand particles surrounded by tangled networks of dislocations impeded the passage of dislocation glide Both experiments focused on the influence of microparticles on dislocation movement because deformed-ice samples have large-sized ice grains. We focused on the relationship between grain-size-sensitive creep and microparticles using samples of the prepared fine-grained ice. By controlling the ice grain sizes and amounts of dispersed microparticles, we could independently investigate the effect of each on the deformation and microstructural evolution of polycrystalline ice. Based on the findings of the deformation experiments and microstructural observations, we discuss the effects of microparticles and GBs on the deformation of ice-sheet ice, and we propose a possible reason for the observed rapid deformation of ice-age ice
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