A Dislocation-Scale Characterization of the Evolution of Deformation Microstructures around Nanoindentation Imprints in a TiAl Alloy

Guitton, Antoine; Kriaa, Hana; Bouzy, Emmanuel; Guyon, Julien; Maloufi, Nabila

doi:10.3390/ma11020305

Cited by 9 publications

(5 citation statements)

References 27 publications

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“…Nanoindentation is an effective method to measure the mechanical properties of materials at the nanoscale, such as the elastic modulus, hardness and strain hardening effect. So far, this technology has been applied to obtain the mechanical properties of various materials including not only pure metals such as Al, Cu, Ag, Ni, and Fe [ 5 , 6 , 7 , 8 ]; but also alloys such as TiAl, U–Cu, Fe–Ni–C, Zr–Cu–Ag–Al and nickel superalloys [ 9 , 10 , 11 , 12 , 13 , 14 , 15 ].…”

Section: Introductionmentioning

confidence: 99%

Nanoindentation of γ-TiAl with Different Crystal Surfaces by Molecular Dynamics Simulations

Fan

Zhou

et al. 2019

Materials

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The periodicity and density of atomic arrangement vary with the crystal orientation, which results in different deformation mechanisms and mechanical properties of γ-TiAl. In this paper, the anisotropic characteristics for γ-TiAl with (100), ( 1 ¯ 10 ) and (111) surfaces during nanoindentation at 300 K have been investigated by molecular dynamics simulations. It is found that there is no obvious pop-in event in all load-depth curves when the initial plastic deformation of γ-TiAl samples occurs, because the dislocation nucleates before the first load-drop; while a peak appears in both the unloading curves of the ( 1 ¯ 10 ) and (111) samples due to the release of energy. Stacking faults, twin boundaries and vacancies are formed in all samples; however, interstitials are formed in the (100) sample, a stacking fault tetrahedron is formed in the (111) sample; and two prismatic dislocation loops with different activities are formed in the ( 1 ¯ 10 ) and (111) samples, respectively. It is also concluded that the values of the critical load, strain energy, hardness and elastic modulus for the (111) sample are the maximum, and for the (100) sample are the minimum. Furthermore, the orientation dependence of the elastic modulus is greater than the hardness and critical load.

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Section: Introductionmentioning

confidence: 99%

Nanoindentation of γ-TiAl with Different Crystal Surfaces by Molecular Dynamics Simulations

Fan

Zhou

et al. 2019

Materials

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“…Figure 1 a is an ECC micrograph of a twin-boundary already characterized by Electron BackScatter Diffraction (EBSD) [ 14 ]. It is carried out using a working distance of 7.3 mm, an acceleration voltage of 10 kV, and a pole piece mounted Backscattered Electron detector in a Zeiss Auriga electronic microscope (Zeiss SEM, Oberkochen, Germany).…”

Section: Methodsmentioning

confidence: 99%

“…Among these techniques, Electron Channeling Contrast Imaging (ECCI) is used in a Scanning Electron Microscope (SEM) for the observation and characterization of these defects in bulk materials [ 9 , 10 , 11 ]. ECCI is a non-destructive technique that provides Transmission Electron Microscope (TEM)-like diffraction contrast imaging of defects [ 10 , 12 , 13 , 14 ]. It is based on the electron channeling phenomenon, where electrons channel down the crystal planes for a given incidence angle between the incident beam and the crystallographic {hkl} planes.…”

Section: Introductionmentioning

confidence: 99%

Modelling Electron Channeling Contrast Intensity of Stacking Fault and Twin Boundary Using Crystal Thickness Effect

2021

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In a scanning electron microscope, the backscattered electron intensity modulations are at the origin of the contrast of like-Kikuchi bands and crystalline defects. The Electron Channeling Contrast Imaging (ECCI) technique is suited for defects characterization at a mesoscale with transmission electron microscopy-like resolution. In order to achieve a better comprehension of ECCI contrasts of twin-boundary and stacking fault, an original theoretical approach based on the dynamical diffraction theory is used. The calculated backscattered electron intensity is explicitly expressed as function of physical and practical parameters controlling the ECCI experiment. Our model allows, first, the study of the specimen thickness effect on the channeling contrast on a perfect crystal, and thus its effect on the formation of like-Kikuchi bands. Then, our theoretical approach is extended to an imperfect crystal containing a planar defect such as twin-boundary and stacking fault, clarifying the intensity oscillations observed in ECC micrographs.

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“…Generally, mechanical testing is preceded and/or followed by microstructural investigations in order to get the structure-property-processing relationships [4,5,6,7]. In situ characterization provides more useful data for a more realistic theoretical modeling, which allows for predicting the mechanical performance of components.…”

Section: Introductionmentioning

confidence: 99%

“…In addition to EBSD analysis, direct SEM observations have been reported while using Electron Channeling Contrast Imaging (ECCI) to characterize for example, cracks in metals, such as NiAl single crystal [16] or also post mortem observation of subgrain-boundaries structures formed in ceramics during deformation [5,17,18].…”

Section: Introductionmentioning

confidence: 99%

In Situ Macroscopic Tensile Testing in SEM and Electron Channeling Contrast Imaging: Pencil Glide Evidenced in a Bulk β-Ti21S Polycrystal

et al. 2019

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In this paper, we report the successful combination of macroscopic uniaxial tensile testing of bulk specimen combined with In situ dislocation-scale observations of the evolution of deformation microstructures during loading at several stress states. The dislocation-scale observations were performed by Accurate Electron Channeling Contrast Imaging in order to follow the defects evolution and their interactions with grain boundaries for several regions of interest during macroscopic loading. With this novel in situ procedure, the slip systems governing the deformation in polycrystalline bulk β-Ti21S are tracked during the macroscopic uniaxial tensile test. For instance, curved slip lines that are associated with “pencil glide” phenomenon and tangled dislocation networks are evidenced.

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A Dislocation-Scale Characterization of the Evolution of Deformation Microstructures around Nanoindentation Imprints in a TiAl Alloy

Cited by 9 publications

References 27 publications

Nanoindentation of γ-TiAl with Different Crystal Surfaces by Molecular Dynamics Simulations

Nanoindentation of γ-TiAl with Different Crystal Surfaces by Molecular Dynamics Simulations

Modelling Electron Channeling Contrast Intensity of Stacking Fault and Twin Boundary Using Crystal Thickness Effect

In Situ Macroscopic Tensile Testing in SEM and Electron Channeling Contrast Imaging: Pencil Glide Evidenced in a Bulk β-Ti21S Polycrystal

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