Using grain boundary irregularity to quantify dynamic recrystallization in ice

Dynamic recrystallization is an important mechanical weakening mechanism during the deformation of ice, yet we currently lack robust quantitative tools for identifying recrystallized grains in “migration” regime that dominates ice at temperatures close to melting point. Here, propose grain boundary irregularity as a means discriminating between (high sphericity, low irregularity) and remnant (low high grains. To this end, analysed cryogenic electron backscatter diffraction (cryo-EBSD) data deformed polycrystalline quantify dynamic using statistics. Grain has inverse relationship with sphericity parameter, Ψ , defined ratio area perimeter, divided by radius 2-D so measurement size independent. Sphericity ( ) typically decreases increasing size, up threshold above which either plateaus (at temperature, T < -10 °C) or increases much more gradually ≥ °C). There no apparent c -axis orientation even very (-4 -5 °C), where GBM dominants, suggesting little crystallographic control on activity migration (GBM). Decreasing can be explained newly-formed, small, spherical growing via strain-induced thereby developing increasingly irregular boundaries. We suggest plateau (or gradual decrease) larger sizes represents population original (i.e., grains) becomes similar rates) due balance nucleation. In interpretation, largest reached end experiment. Thus, provides grains—a capability potentially useful evaluating processes The experiment duration used calculate rates evolution associated GBM. are temperatures, rates. Previous studies show mobility decreasing temperature. driving force GBM, other hand, positive correlation stress, temperature if strain rate remains unchanged. likely cause temperatures.