Intragranular plasticity vs. grain boundary sliding (GBS) in forsterite: Microstructural evidence at high pressures (3.5–5.0 GPa)

Bollinger, Caroline; Marquardt, Katharina; Ferreira, Filippe

doi:10.2138/am-2019-6629

Cited by 18 publications

(24 citation statements)

References 58 publications

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“…The microstructure observed in Fig. 13 is comparable to those reported in polycrystalline copper (Miura et al, 2007) and ice (Chauve et al, 2017), which were interpreted as nuclei for neograins during discontinuous dynamic recrystallization (dDRX). This mechanism has also been identified recently by Bollinger et al (2019a) in polycrystalline forsterite deformed at high pressure (3.5-5 GPa) to large strains (25 %-40 %).…”

Section: Dynamics Recrystallizationsupporting

confidence: 72%

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Characterization of recovery onset by subgrain and grain boundary migration in experimentally deformed polycrystalline olivine

et al. 2020

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To apprehend plate tectonics and the dynamics of the lithosphere-asthenosphere boundary, composed principally of olivine, we need to understand the mechanisms that control plastic deformation of olivine in the relevant temperature domain. After more than 50 years of laboratory studies and investigations on natural rocks, the interplay of several key parameters (e.g. temperature, pressure, vacancy concentration, dislocation densities, grain size, strain rate) controlling polycrystalline olivine plasticity remains difficult to assess. Here, we study four olivine polycrystals, which have been deformed in axial compression under a confining pressure of 300 MPa, at 1273 or 1473 K. Despite significant differences in mechanical properties (stress-strain curves), previous characterization by scanning (SEM) and transmission electron microscopy (TEM) did not reveal significant differences in dislocation microstructures which could explain these contrasted behaviours. We have undertaken automatic crystallographic orientation mapping (ACOM) analyses in TEM to increase the spatial resolution of characterization compared to previously obtained electron backscatter diffraction maps to further decipher the microstructures at nanoscale. With this novel technique applied to olivine, a noticeable difference in the onset of microstructural recovery has been identified between specimens deformed at 1273 and 1473 K. The microstructures of the olivine polycrystals deformed at 1473 K exhibit numerous curved grain and subgrain boundaries, advocating for recovery by boundary migration. In contrast, the microstructures of the olivine polycrystals deformed at 1273 K have significantly fewer subgrain boundaries and show more straight boundaries (i.e. closer to an equilibrium microstructure) than in the specimen deformed at 1473 K. Characterization by ACOM-TEM has permitted the identification of the onset of recovery, which is led by boundary migration even for very low macroscopic finite strains. liths or tectonic massifs (e.g.

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Section: Dynamics Recrystallizationsupporting

confidence: 72%

“…Yet, this issue is still under debate as its applicability to upper mantle remains very specific (e.g. Platt and Behr, 2011;Bollinger et al, 2019b;Gasc et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Characterization of recovery onset by subgrain and grain boundary migration in experimentally deformed polycrystalline olivine

et al. 2020

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“…Grain boundary sliding is often invoked as a source of high strain gradients at the GBs. Microstructural evidence for sliding at GBs have indeed been reported in olivine, either deformed in the diffusion creep regime [45,46] or in the dislocation creep regime [18]. However, in the present post mortem study, we did not have a marker to confirm or dismiss the possible contribution of GBs in the nucleation of new grains.…”

Section: Discussioncontrasting

confidence: 42%

“…Experimental set up, data analysis, and results for sample For70B have been previously reported in [16][17][18] for sample M642. The following section is hence limited to the most relevant information regarding the present study.…”

Section: Methodsmentioning

confidence: 99%

Microstructural Evidence for Grain Boundary Migration and Dynamic Recrystallization in Experimentally Deformed Forsterite Aggregates

et al. 2018

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Plastic deformation of peridotites in the mantle involves large strains. Orthorhombic olivine does not have enough slip systems to satisfy the von Mises criterion, leading to strong hardening when polycrystals are deformed at rather low temperatures (i.e., below 1200 °C). In this study, we focused on the recovery mechanisms involving grain boundaries and recrystallization. We investigated forsterite samples deformed at large strains at 1100 °C. The deformed microstructures were characterized by transmission electron microscopy using orientation mapping techniques (ACOM-TEM). With this technique, we increased the spatial resolution of characterization compared to standard electron backscatter diffraction (EBSD) maps to further decipher the microstructures at nanoscale. After a plastic strain of 25%, we found pervasive evidence for serrated grain and subgrain boundaries. We interpreted these microstructural features as evidence of occurrences of grain boundary migration mechanisms. Evaluating the driving forces for grain/subgrain boundary motion, we found that the surface tension driving forces were often greater than the strain energy driving force. At larger strains (40%), we found pervasive evidence for discontinuous dynamic recrystallization (dDRX), with nucleation of new grains at grain boundaries. The observations reveal that subgrain migration and grain boundary bulging contribute to the nucleation of new grains. These mechanisms are probably critical to allow peridotitic rocks to achieve large strains under a steady-state regime in the lithospheric mantle.

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“…This grain size sensitive mechanism may be important in inducing strain localization in the lithosphere 6 . GBS is identified by displacements across grain boundaries which have been observed in high-temperature deformation experiments in the diffusion creep regime 7 , and in the dislocation creep regime 8 . Grain boundary sliding also operates under high confining pressure (3-5 GPa) relevant for the base of the continental lithosphere [8][9][10] .…”

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confidence: 99%

Stress-induced amorphization triggers deformation in the lithospheric mantle

Samae

Cordier

Demouchy

et al. 2021

Nature

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Intragranular plasticity vs. grain boundary sliding (GBS) in forsterite: Microstructural evidence at high pressures (3.5–5.0 GPa)

Cited by 18 publications

References 58 publications

Characterization of recovery onset by subgrain and grain boundary migration in experimentally deformed polycrystalline olivine

Characterization of recovery onset by subgrain and grain boundary migration in experimentally deformed polycrystalline olivine

Microstructural Evidence for Grain Boundary Migration and Dynamic Recrystallization in Experimentally Deformed Forsterite Aggregates

Stress-induced amorphization triggers deformation in the lithospheric mantle

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