Modeling the creep properties of olivine by 2.5-dimensional dislocation dynamics simulations

Abstract

In this work we performed 2.5-dimensional (2.5D) dislocation dynamics simulations coupling climb with the glide dislocation motion to model the creep behavior of olivine, one of the main component of the Earth's upper mantle. In particular, we present an application of this method to determine the creep strain rate in a material with high lattice resistance, such as olivine. We show that by including the climb mechanism we reach steady state creep conditions. Moreover, we find that a creep power law with a stress exponent close to 3 can be extracted from our simulations and we provide a model based on Orowan's law to predict the creep strain rates in the high temperature and low stress regime. The model presented is relevant to describe the plastic flow of olivine in the Earth's mantle deformation conditions and can be useful to derive the high temperature creep behavior of other materials.

Dislocations and Plastic Deformation in MgO Crystals: A Review

“…In addition to the work of Cordier's group for mineral physics applications [23,45,126,127,[130][131][132], one can refer to the work of Chang and coworkers who investigated the plastic deformation of <111>-oriented LiF micropillars from room temperature up to 600 K [113]. In this study, DD simulations predict a size-dependent flow stress in the micrometer-size regime ("smaller is stronger") in good agreement with experimental results [133], see also Section 4.5.…”

“…Due to the additional computational cost associated with modeling diffusion, the models used are usually based on 2.5D simulations [131,134]. An illustration is presented in Figure 12.…”

Dislocation Interactions in Olivine Revealed by HR‐EBSD

“…Experiments designed specifically to investigate dislocation interactions in single crystals of olivine at 1550–1600°C found no evidence that interactions between dislocation types modified either the microstructures or mechanical properties compared to those generated by activation of single slip systems in isolation (Durham et al, ). However, TEM observations and modeling suggest that interactions between dislocations may modify glide behavior at temperatures of 800–1000°C (Boioli, Carrez, et al, ; Boioli, Tommasi, et al, ; Durinck et al, ; Mussi et al, ). Our analysis of olivine deformed at 1000°C and 1200°C strongly suggests that interactions between different dislocation types hindered dislocation glide, impacted the development of substructure, and thereby presumably exerted an influence on mechanical properties.…”

Stress evolution and associated microstructure during transient creep of olivine at 1000–1200 °C

“…The maximum stresses from our experiments at 1000 °C and existing low temperature (exponentional) flow laws are shown in Figure 12c. The maximum stress for 1.1 % of finite strain at 1000 °C (CMT16-8, no steady state or brittle failure) surpasses recent calculations based on 2.5-D dislocation dynamics models for single crystals of olivine oriented for easy slip (Boioli et al 2015; their Figure 3). In this study, they model a single glide direction, [100](001), in a olivine single crystal, therefore giving only a lower bound of the strength.…”

“…We conclude that the sample CMT17-2 deformed in the brittle field by micro fracturing for a strain > 3% (at 1127 MPa, where the cuve flattens abruptly), while the other samples underwent no brittle failure. Rigid body grain rotation cannot be observed, since the , Chopra & Paterson (1984), Hirth & Kohlstedt (2003), Raterron et al (2004), Keefner et al (2011, Demouchy et al (2013), Boioli et al (2015), Idrissi et al (2016), Tielke et al (2016, shear on (100)[001] for 1000 °C and (001)[100] for 1200 °C) and Tielke et al (2017, dry/wet glide for 1000 °C and wet climb for 1200 °C, 11-16 ppm H2O wt. or 190-260 ppm H/10 6 Si).…”