Strain field evolution during dynamic recrystallization nucleation; A case study on ice

Nucleation mechanisms occurring during discontinuous dynamic recrystallization (DDRX) is investigated by Digital Image Correlation (DIC) during creep experiment on polycrystalline columnar ice. Thanks to the columnar microstructure, discrimination of the nucleus can be done without ambiguity comparing pre- and post- deformation texture. In-situ DIC analyses are performed around a triple junction were nucleation occurred to follow strain field evolution. Strain field evolution appears strongly linked to nucleation mechanisms, local grain boundary migration and sub-grain boundary formation such as tilt sub-grain boundaries and kink bands. Nucleation processes are correlated with strong strain heterogeneities well characterized by the principal strains evaluated by DIC. It was possible to follow nucleus growth through the evolution of strain localization along the new grain boundaries. Kink bands act as a buffer zone close to the triple junction and accommodate shear parallel to the c-axis. The local strain field appears to be efficiently redistributed by recrystallization processes which create a new microstructure more compatible with the local stresses. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.