Characterization of the glide planes of the [001] screw dislocations in olivine using electron tomography

Mussi, Alexandre; Cordier, Patrick; Demouchy, Sylvie; Vanmansart, Claude

doi:10.1007/s00269-014-0665-1

Cited by 37 publications

(42 citation statements)

References 45 publications

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“…Having orthogonal Burgers vectors, dislocations from these slip systems have a very weak propensity to form junctions (e.g. Durinck et al, 2007;Mussi et al, 2015). Hence the tendency for dislocation storage is lower than in other crystallographic structures such as cubic metals; indeed, we did not observe a clear correlation between the total finite plastic strain and the dislocation density.…”

Section: Strain-hardening Versus Thermally Activated Recoverycontrasting

confidence: 52%

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: Strain-hardening Versus Thermally Activated Recoverycontrasting

confidence: 52%

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

et al. 2020

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“…Deformation of olivine in the climb‐controlled regime involves simultaneous operation of multiple dislocation slip systems. At high‐temperature, low‐stress conditions in the climb‐controlled regime, deformation occurs primarily by the motion of dislocations on the (010)[100], (001)[100], (100)[001], and (010)[001] slip systems with possible additional activation of the (0kl)[001] and (110)[001] systems [ Durham and Goetze , ; Durham et al , ; Mussi et al , , ]. The [101] c orientation used in this study produces no resolved shear stress on dislocation slip systems that involve glide on the (010) plane, so that the contribution of the (010)[100] and (010)[001] slip systems to the strain rate is negligible.…”

Section: Discussionmentioning

confidence: 99%

“…Plot of the strain rates predicted using the flow law parameters for wet (hydrous) or dry (anhydrous) deformation. The wet power law is from equation (16), the flow law for Tielke et al [2016] is a sum of the power laws for crystals deformed under anhydrous conditions and oriented for shear on (001)[100] and (100)[001] from Tielke et al [2016], the relationship from Bai et al [1991] are for crystals in the [101] c orientation under anhydrous conditions, and the exponential relationship is equation (17). with possible additional activation of the (0kl)[001] and (110)[001] systems Mussi et al, 2014Mussi et al, , 2015. The [101] c orientation used in this study produces no resolved shear stress on dislocation slip systems that involve glide on the (010) plane, so that the contribution of the (010)[100] and (010)[001] slip systems to the strain rate is negligible.…”

Section: Microstructural Observationsmentioning

confidence: 99%

Hydrolytic weakening in olivine single crystals

2017

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Deformation experiments on single crystals of San Carlos olivine under hydrous conditions were performed to investigate the microphysical processes responsible for hydrolytic weakening during dislocation creep. Hydrogen was supplied to the crystals using either talc or brucite sealed in nickel capsules with the crystal. Deformation experiments were carried out using a gas medium apparatus at temperatures of 1050° to 1250°C, a confining pressure of 300 MPa, differential stresses of 45 to 294 MPa, and resultant strain rates of 1.5 × 10−6 to 4.4 × 10−4 s−1. For talc‐buffered (i.e., water and orthopyroxene‐buffered) samples at high temperatures, the dependence of strain rate on stress follows a power law relationship with a stress exponent (n) of ∼2.5 and an activation energy of ∼490 kJ/mol. Brucite‐buffered samples deformed faster than talc‐buffered samples but contained similar hydrogen concentrations, demonstrating that strain rate is influenced by orthopyroxene activity under hydrous conditions. The values of n and dependence of strain rate on orthopyroxene activity are consistent with hydrolytic weakening occurring in the climb‐controlled dislocation creep regime that is associated with deformation controlled by lattice diffusion under hydrous conditions and by pipe diffusion under anhydrous conditions. Analyses of postdeformation electron‐backscatter diffraction data demonstrate that dislocations with [100] Burgers vectors are dominant in the climb‐controlled regime and dislocations with [001] are dominant in the glide‐controlled regime. Comparison of the experimentally determined constitutive equations demonstrates that under hydrous conditions crystals deform 1 to 2 orders of magnitude faster than under anhydrous conditions.

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“…">DiscussionElectron tomography, which can reach angular resolution of 2°, is a powerful technique to characterize glide planes [20,23,[29][30][31][32][33][34][35][36][37], cross-slip [23,36], climb planes and dislocation interactions. In a previous study, we established that in olivine,   001 dislocations could glide in   120 and   130 [23]. We show in figure 3(c) that   001 dislocations can also glide in 140   .We report here, to the best of our knowledge, the first unequivocal evidence of 101 junctions in olivine.…”

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confidence: 99%

Characterization of dislocation interactions in olivine using electron tomography

Mussi¹,

Demouchy²

2015

Philosophical Magazine

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We have investigated by electron tomography, in a transmission electronic microscope, the interactions between dislocations in olivine single crystals and polycrystals deformed in axial compression at T < 1000 °C (T < 0.5Tm). Dislocations are mostly of the [0 0 1] type, except in the polycrystal where [1 0 0] and [0 0 1] dislocations have been activated. A few 〈1 0 1〉 junctions have been found and characterized. Many collinear interactions have been identified either involving direct interactions between crossing dislocations of opposite Burgers vectors or indirect interactions between dislocations gliding in parallel planes and sessile dislocation loops. We suggest that collinear interaction, already identified as the primary source of strain hardening in FCC metals, is the main dislocation interaction mechanism in olivine deformed at temperatures below 1000 °C

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Characterization of the glide planes of the [001] screw dislocations in olivine using electron tomography

Cited by 37 publications

References 45 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

Hydrolytic weakening in olivine single crystals

Characterization of dislocation interactions in olivine using electron tomography

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