Subgrain Rotation Recrystallization During Shearing: Insights From Full‐Field Numerical Simulations of Halite Polycrystals

Abstract

We present, for the first time, results of full‐field numerical simulations of subgrain rotation recrystallization of halite polycrystals during simple shear deformation. The series of simulations show how microstructures are controlled by the competition between (i) grain size reduction by creep by dislocation glide and (ii) intracrystalline recovery encompassing subgrain coarsening by coalescence through rotation and alignment of the lattices of neighboring subgrains. A strong grain size reduction develops in models without intracrystalline recovery, as a result of the formation of high‐angle grain boundaries when local misorientations exceed 15°. The activation of subgrain coarsening associated with recovery decreases the stored strain energy and results in grains with low intracrystalline heterogeneities. However, this type of recrystallization does not significantly modify crystal preferred orientations. Lattice orientation and grain boundary maps reveal that this full‐field modeling approach is able to successfully reproduce the evolution of dry halite microstructures from laboratory deformation experiments, thus opening new opportunities in this field of research. We demonstrate how the mean subgrain boundary misorientations can be used to estimate the strain accommodated by dislocation glide using a universal scaling exponent of about 2/3, as predicted by theoretical models. In addition, this strain gauge can be potentially applied to estimate the intensity of intracrystalline recovery, associated with temperature, using quantitative crystallographic analyses in areas with strain gradients.

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

“…Subgrain rotation is a process that involves an increase in the misorientation across the subgrain boundary resulting from continuous addition of dislocations (Lallemant, 1985;Placidi et al, 2004). New grains will form as the misorientation across the subgrain boundary becomes large enough, with the subgrain boundary eventually dividing its parent grain (Poirier and Nicolas, 1975;Guillope and Poirier, 1979;Urai et al, 1986;Gomez-Rivas et al, 2017). This process is known as the subgrain rotation recrystallization (Hirth and Tullis, 1992;Stipp et al, 2002;Passchier and Trouw, 2005).…”

Time for anisotropy: The significance of mechanical anisotropy for the development of deformation structures

“…In geology the coupling of the full-field crystal plasticity VPFFT (Viscoplastic Full-Field Transform) method by , and the ELLE microstructural simulation platform Bons et al, 2008;; http://www.elle.ws) has allowed the systematic simulation of deformation and recrystallization of polycrystalline rocks (such as ice and halite, e.g. Llorens et al, 2016a,b;Gomez-Rivas et al, 2017). In these cases, the polycrystalline aggregate is discretised into a periodic, regular mesh of nodes that store properties such as lattice orientation and dislocation density.…”

The effect of dynamic recrystallisation on the rheology and microstructures of partially molten rocks

“…ELLE couples different processes acting on the microstructure in a sequential order for small time steps (Jessell et al, 2001). ELLE has been applied to a range of problems in geology (Bons et al, 2008), of which the most relevant to this study are simulations of static and dynamic grain boundary migration in single and twophase materials (Bons et al, 2001;Becker et al, 2008;Roessiger et al, 2011;Roessiger et al, 2014;Ran et al, 2018) and viscous or viscoplastic deformation either as a single process (Bons and Cox, 1994;Jessell et al, 2009;Griera et al, 2013;Llorens et al, 2013a;2013b) or coupled with dynamic recrystallisation (Llorens et al, 2016a;2016b;2017;Steinbach et al, 2016;2017;Gomez-Rivas et al, 2017). Jessell et al (2009) and Ran et al (2018) carried out a series of deformation simulations of two-phase aggregates up to relatively high shear strains.…”

“…The VPFFT formulation provides a solution of the micromechanical problem by finding a strain rate and stress field that minimises the average local work-rate under the compatibility and equilibrium constraints (see Lebensohn, 2001). The deformation-induced lattice rotation and the estimation of geometrically necessary dislocation (GND) densities calculated from the stress and velocity field are provided by the VPFFT (Llorens et al, 2016a;2016b;2017;Steinbach et al, 2016;2017;Gomez-Rivas et al, 2017). The GND density associated with the lattice distortion (Ashby, 1970) is calculated from the plastic strain gradient (derived from Gao et al, 1999) assuming a constant Burger's vector for all slip systems (see Llorens et al, 2016a for a detailed description of the method).…”