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

Slama, Meriem Ben Haj; Maloufi, Nabila; Guyon, Julien; Bahi, Slim; Weiss, Laurent; Guitton, Antoine

doi:10.3390/ma12152479

Cited by 12 publications

(9 citation statements)

References 37 publications

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“…As reported in our previous work [23] detailing the experimental procedure: Bulk tensile sample ( Fig. 1 a) was cut from a 1.78 mm thickness rolled sheet of -Ti21S alloy, produced by Titanium Metals Corporation / Toronto, Canada.…”

Section: Materials and Experimental Setupmentioning

confidence: 99%

“…After yielding and a few percent strain, the resulting microstructure is slightly deformed. Such a microstructure is investigated using A-ECCI to maximize the contrast from slip lines and dislocations [23] .…”

Section: Slip Trace Analysismentioning

confidence: 99%

“…A more powerful technique, Accurate Electron Channeling Contrast Imaging (A-ECCI) developed some years ago [21] , has an angular accuracy better than 0.1°with a spatial resolution finer than 500 nm [22] . By coupling A-ECCI to an in situ tensile test inside the SEM [23] , several areas on a bulk sample can be accessed with a single tool while under mechanical load, thus covering the scale from sample to dislocations. The availability of multiple regions of interest is helpful in enumerating relevant statistical parameters from the mesoscopic and microscopic descriptions of microstructures, which in turn provides large enough datasets for data mining.…”

Section: Introductionmentioning

confidence: 99%

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Electron channeling contrast imaging characterization and crystal plasticity modelling of dislocation activity in Ti21S BCC material

et al. 2021

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In this paper, an original approach is proposed to compare modeling and relevant statistical experiments using -Ti21S Body Centered Cubic (BCC) metal as a challenging benchmark. Our procedure allows the evolution of microstructural defects to be tracked in situ with excellent spatial resolution, while observing a bulk sample region sufficiently large to be statistically representative of the material. We identify multiple mechanisms such as slip transfer, slip traces, pencil glide, etc. We demonstrate that for small plastic strains ( < 0.25 %) under uniaxial tensile loading, the Schmid law is satisfied statistically. Under these circumstances, changes in Critical Resolved Shear Stress (CRSS) are minimal and accommodation of incompatible deformation between grains has not yet become important. The majority of the observed slip plane traces at the mesoscale corresponds to the {123} family. Fully automated while precise, the reported approach compares this data with four crystal plasticity models, and provides a methodology for similar analyses in other materials. * Corresponding author. X-Ray Diffraction HR-XRD, Electron BackScattered Diffraction EBSD…) that provide valuable atomic scale information, such as activation energies and critical shear stresses. However, one may argue that most multiscale strategies usually address only very specific cases, and that they are not necessarily statistically representative of the myriad of mechanisms that can occur in real polycrystals. For instance, one can cite HR-TEM [4] studies of special grain boundaries (structure, energy, migration under stress and temperature…) and their interactions with dislocations (emission, absorption, transmission…). Indeed, such available studies are far from covering the full range of possible grain boundary configurations in a real polycrystal. In addition, preparing and testing of thin foils for electron transmission-based techniques [5-7] (TEM, Transmission Kikuchi Diffraction TKD) can unfortunately affect the defect microstructure and the mechanisms investigated because of inherent size, strain rate, and external surface effects. Besides, these techniques do not provide enough data for statistical analysis of physical mechanisms.Experimental findings at an intermediate, mesoscopic scale, can be used to improve our knowledge of polycrystal plasticity and to improve models at the grain scale. They provide validation data for advanced numerical simulations that predict the mechanical behavior of polycrystals (strain hardening, ductility etc.

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Section: Materials and Experimental Setupmentioning

confidence: 99%

Section: Slip Trace Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electron channeling contrast imaging characterization and crystal plasticity modelling of dislocation activity in Ti21S BCC material

et al. 2021

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“…Non-crystallographic slip has also been observed where dislocations glide onto the potentially non-crystallographic plane with the maximum resolved shear stress [40]. Finally, cross-slip is often reported where dislocations move from one plane to another and leave curved marks on the surface, known as "pencil glide" [41]. In α-Fe, recent investigations of slip in ferrite single-crystals suggest preferential slip on the {110}<111> and {112}<111> slip systems, at room temperature and in quasi-static conditions [42].…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of early strain heterogeneities and localizations in polycrystalline α-Fe during monotonic loading

Berger

Witz

Bartali

et al. 2022

International Journal of Plasticity

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“…An optimized procedure referred as Accurate Electron Channeling Contrast Imaging (A-ECCI), and based on the precise control of the channeling conditions taking advantage of the 0.1° angular resolution of High Resolution Selected Area Channeling Patterns with an improved spatial resolution of 500nm was developed some years ago [27], [28], [30], [31]. A-ECCI thus enables the comprehensive characterization of defects such as stacking faults or dislocations, and can be used in conjunction with in situ tensile test inside the SEM [32], [33]. This technique provides access to multiple regions of interest; from sample scale to dislocation scale; with one unique tool while loading a bulk sample, thus providing access to large datasets amenable to the application of data mining procedures.…”

Section: Introductionmentioning

confidence: 99%

Tuning critical resolved shear stress ratios for bcc-titanium Ti21S via an automated data analysis approach

Venkatraman¹,

Slama²,

Taupin³

et al. 2021

Modelling Simul. Mater. Sci. Eng.

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We introduce a novel method for automated slip trace detection and analysis based on the Hough transform algorithm and apply it to Electron Channelling Contrast Imaging micrographs. This is further augmented with an automation procedure for the determination of slip-trace crystallography in conjunction with orientation data acquired via electron backscattered diffraction. Automation is required for faster indexation of the slip traces and for more reliable statistical studies. The automation procedure was applied to different regions of interest on a β-Ti21S sample loaded in situ in tension. β-Ti21S is a BCC alloy with 48 slip systems available to accommodate plastic deformation, including all complexities associated with pencil glide. Multiple regions of interest were analyzed using the automation procedure. The acquired slip distribution statistics reveals that the majority of the slip traces belong to the {112} and {123} slip families. The deformation response of the observed regions of interest was also simulated using a fullfield crystal plasticity model implemented in DAMASK, based on a phenomenological power law based constitutive formulation, incorporating all potentially active 48 slip systems. The slip system activity distribution from modelling is compared with the slip distribution statistics observed experimentally. The plasticity parameters for β-Ti21S were taken from the literature and the Critically Resolved Shear Stress (CRSS) values were adjusted to match the experimentally observed yield stress value. We begin with uniform CRSS ratios for all three potential slip system families and tune the CRSS ratios to match the slip-distribution statistics experimentally, keeping the average CRSS value the same for all cases. Thus, a method has been introduced to tune average CRSS values and ratios by considering both the macroscopic stress-strain response and the locally observed slip-distribution statistics, obtained via automated slip trace detection procedure.

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

Cited by 12 publications

References 37 publications

Electron channeling contrast imaging characterization and crystal plasticity modelling of dislocation activity in Ti21S BCC material

Electron channeling contrast imaging characterization and crystal plasticity modelling of dislocation activity in Ti21S BCC material

Experimental investigation of early strain heterogeneities and localizations in polycrystalline α-Fe during monotonic loading

Tuning critical resolved shear stress ratios for bcc-titanium Ti21S via an automated data analysis approach

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