Dynamic dislocation–defect analysis

Saimoto, S.

doi:10.1080/14786430500367347

Cited by 37 publications

(33 citation statements)

References 39 publications

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“…Strain rate sensitivity using thermal cycling between 78-162 K shows that [001] which includes both primary-critical and the primary-conjugate combinations show lower strain rate sensitivity than [111] which encompass only the primary-conjugate pairs. On the other hand for the 78-273 K cycling, the response are identical showing that the primary-critical obstacle formation, that is jogdragging, has ceased due to formation of Stroh-Hirth locks [9] as indicated above.…”

Section: Multiple Slip Effects In Copper Single Crystals Under Homogementioning

confidence: 53%

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Decoding Pattern Dependence of Micro-indentation on Crystal Orientation of Cube-textured Aluminum Foil Using SAXS and Temperature Changes

Saimoto

Singh

Langille

et al. 2018

IOP Conf. Ser.: Mater. Sci. Eng.

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Recent use of nano-indentation to assess work-hardening of complex microstructure of dual phase steels as a function of deformation together with crystal plasticity finite element method to simulate the bulk properties gives rise to the question of the role of crystallite orientation during indentation. Such studies using nano-indentation on µm-sized grains are difficult. To elucidate this effect, Vickers microindentation of cube textured Al capacitor foils were examined. These foils of 106 µm thickness are convenient for small angle X-ray scattering (SAXS) examination and the orientation around the indent can be examined by back-scattered electron diffraction (EBSD). The indentations were carried out with the diagonals parallel to the rolling direction (RD) and 45 ° to it at temperatures from 20 °C (295 K) to 160°C (433 K). The SAXS tests were performed only at 20°C on RD specimens.Keywords: Aluminum, micro-hardness, SAXS, stacking fault tetrahedral, dislocation intersections IntroductionIndentation testing using Vickers hardness with diamond pyramid head has been the standby materials characterization of mechanical properties. Since the discovery of age-hardenable alloys, the great progress is due to the advent of hardness testing to monitor ageing as function of time and annealing temperatures and has become the standard procedure to perform such tests to delineate the optimum hardness for alloy development. As the microstructure of the alloy becomes more complex with multiple hardening precipitates, the indenter size have decreased to micro-and nano-meter scales. Detailed characterization of texture and stored work in damaged volumes using conical indenter have been performed to determine if a simple correlation between hardness and geometric-necessary-dislocation (GND) density exist [1]. The application of such computational analyses was recently illustrated for dual-phase steels [2] in which nano-indentation result was used to correlate to the bulk stress-strain response. However application of such methods to face-centred cubic (fcc) structures may require more statistical testing to assess the crystal orientation dependence of the hardness response. Hardness has been attributed to two main factors; the yield strength due to the size, density and distribution of the embedded nano-particles and the gradients in GND densities around the indent interface. Brown [3] has simulated indentation using Vickers diamond indenter and has developed a circular flow model to predict lattice rotation which could rise as high as 12 °. Such rotations has been observed in Berkovichtip indented matrix of cube oriented copper crystal using Kikuchi line analysis of electron diffraction (TEM) images (14 °) [4] and in conical indented (111) surface of copper crystal (15 °) using EBSD [1]. Although the analytical means for modelling micro-and nano-plastic flow seems to be at hand [2], for aluminum (Al) alloys dynamic recovery can occur during indentation at room temperatures.During the recent work of assessing double Brag...

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Section: Multiple Slip Effects In Copper Single Crystals Under Homogementioning

confidence: 53%

“…These serrations coincided with the appearance of slip lines [9] on the (110) surface wherein three traces are observed with the third and fourth being coincidental. This instability was attributed to strain ageing due to atmosphere formation by vacancies.…”

Section: Multiple Slip Effects In Aluminum Single Crystalsmentioning

confidence: 94%

Decoding Pattern Dependence of Micro-indentation on Crystal Orientation of Cube-textured Aluminum Foil Using SAXS and Temperature Changes

Saimoto

Singh

Langille

et al. 2018

IOP Conf. Ser.: Mater. Sci. Eng.

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“…The described CRA became possible upon discovering a way to calibrate the mean slip distance k: 10,16 k ¼ u b l 2 @c=2s @s T;_ c j ð1Þ whereby the flow shear stress s is determined from (r À r 0 final )/M; the shear strain, c = Me in which M is the Taylor factor; l, the shear modulus; b, the Burgers vector; and u, the calibration factor is derived from h cal = ¶s/ ¶c at 0.2% e given as 1/u = (l/h cal )/2a. The derived yield stress r 0 final is determined by backextrapolation.…”

Section: Constitutive Relation Analysis (Cra)mentioning

confidence: 99%

Constitutive Relations Analyses of Plastic Flow in Dual-Phase Steels to Elucidate Structure–Strength–Ductility Correlations

Saimoto

Timokhina

Pereloma

2017

JOM

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The structure-strength characterization is typically performed by correlating the structure with x-ray, electron, or atomic imaging devices to the bulk mechanical tensile parameters of yield stress and the plastic yielding response. The problem is that structure parameters embedded in the stressstrain data cannot be revealed without an analyzable constitutive relation. New functional slip-based constitutive formulation with precise digital fitting parameters can replicate the measured data with at least two loci. Thus, this study examines the possibility of identifying the mechanical response as a result of the various microstructure components. The key parameter, the mean slip distance, can be calibrated from the initial work-hardening slope at 0.2% strain from which all the fit parameters can be determined. In this process, a newly derived friction stress is defined to separate the yield phenomenon from the plastic strains beyond yield-point elongation. This methodology has been applied to dual-phase steel specimens that resulted in excellent predictive correlations with prior structure-strength characterization. Hence, the structure-strength-ductility changes resulting from processing conditions can be more precisely surmised from mechanical testing. Thus, a method to delineate the nanostructure evolution with deformation using mesoscopic mechanical parameters has been introduced.

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“…One of us has been pursuing this type of representation and has shown that a differential form of the modified Hollomon relation [10] is found at strains beyond 4% for polycrystalline Al [11]. Recently it was realized that a quantitative relation of k and (sos/oc) À1 is possible as suggested by theoretical analysis using the initial slope for [1 0 0] single-crystal tensile tests [12]. This quantitative determination of k from the dynamic r-e curve implies that a correlation between c and k can be obtained by plotting log k vs. log s. The described development will show that the k-proportionality constant for polycrystalline material can be directly determined from the r-e curve according to the methodology described.…”

Section: Introductionmentioning

confidence: 98%

“…and its value has been evaluated from Stage II h II type determination of [1 0 0] single crystals [12]. Thus, in principle, k is determinable as a function of s or c. Based on this premise, the computation of new lengths that is created to produce an incremental strain of Dc is possible as shown below.…”

Section: Derivation Of Constitutive Relations Based On Concepts Intromentioning

confidence: 99%

Constitutive relation based on Taylor slip analysis to replicate work-hardening evolution

Saimoto

Houtte

2011

Acta Materialia

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Dynamic dislocation–defect analysis

Cited by 37 publications

References 39 publications

Decoding Pattern Dependence of Micro-indentation on Crystal Orientation of Cube-textured Aluminum Foil Using SAXS and Temperature Changes

Decoding Pattern Dependence of Micro-indentation on Crystal Orientation of Cube-textured Aluminum Foil Using SAXS and Temperature Changes

Constitutive Relations Analyses of Plastic Flow in Dual-Phase Steels to Elucidate Structure–Strength–Ductility Correlations

Constitutive relation based on Taylor slip analysis to replicate work-hardening evolution

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