Finite element simulation of interfacial segregation in dilute alloys

Chabert, Florent Fournier Dit; Tancret, Franck; Christien, Frédéric; Gall, René Le; Castagne, J. L.

doi:10.1007/s10853-007-2001-3

Cited by 12 publications

(7 citation statements)

References 10 publications

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“…Thus, the Ga accumulations are not related to the formation of Ga precipitates due to phase separation between Ga and Ge (Gokhale & Abbaschian, 1990), but to Ga segregation on dislocation loops, explaining the observation of Ga accumulations for Ga concentrations below the solubility limit in Ge. The increase of Ga solute atom concentration with temperature is not related to the increase of Ga solubility with temperature, as is usually assumed from the SIMS measurements, but to the usual decrease of the equilibrium segregation driving force when the temperature increases (Portavoce et al, 2004 a ; Fournier Dit Chabert et al, 2007). In the present case, the diffusion model used to determine the Ga diffusion coefficients from the fit of the experimental SIMS profiles should not include precipitation but segregation on dislocation loops.…”

Section: Resultsmentioning

confidence: 98%

Coupling Secondary Ion Mass Spectrometry and Atom Probe Tomography for Atomic Diffusion and Segregation Measurements

2019

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For a long time, secondary ion mass spectrometry (SIMS) was the only technique allowing impurity concentrations below 1 at% to be precisely measured in a sample with a depth resolution of few nanometers. For example, SIMS is the classical technique used in microelectronics to study dopant distribution in semiconductors and became, after radiotracers were forsaken, the principal tool used for atomic transport characterization (diffusion coefficient measurements). Due to the lack of other equivalent techniques, sometimes SIMS could be used erroneously, especially when the analyzed solute atoms formed clusters, or for interfacial concentration measurements (segregation coefficient measurements) for example. Today, concentration profiles measured by atom probe tomography (APT) can be compared to SIMS profiles and allow the accuracy of SIMS measurements to be better evaluated. However, APT measurements can also carry artifacts and limitations that can be investigated by SIMS. After a summary of SIMS and APT measurement advantages and disadvantages, the complementarity of these two techniques is discussed, particularly in the case of experiments aiming to measure diffusion and segregation coefficients.

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Section: Resultsmentioning

confidence: 98%

Coupling Secondary Ion Mass Spectrometry and Atom Probe Tomography for Atomic Diffusion and Segregation Measurements

2019

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“…This methodology is applied to a fatigue test specimen with a cylindrical geometry (3.11 mm radius). Room temperature behavior has been calculated using the anisotropic elasto-viscoplatic model developed for the AMl superalloy [18]. Figure 8 represents the hoop (aee) and axial (azz) stresses in a quarter of crosssection just after shot-peening.…”

Section: Internal Variables Initializationmentioning

confidence: 99%

Influence of Residual Stresses on the Fatigue Life of a Shot‐Peened Nickel‐Based Single Crystal Superalloy: From Measurements to Modeling

et al. 2016

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In this work, X-ray diffraction measurements and finite elements calculations are combined to investigate the effect of the shot-peening process on the fatigue lifetime of the AMI nickel-based single crystal superalloy. The Ortner method is used to determine residual elastic stress depth profiles in plane-parallel samples. They exhibit a I30-I60 µm thick hardened layer where there are compressive stresses up to 1000-I400 MPa. The tensile stresses which ensure the mechanical equilibrium of the samples are not localized in a specific layer but rather distributed in a few millimeters thick layer. The eigenstrain theory is then used to incorporate measured stresses in the elasto-viscoplatic modeling of shot-peened fatigue test specimens. A numerical method is proposed to initialize hardening variables in the shot-peened layer independently of the complexity of the constitutive law or measurements in calibration samples. Finally, a fatigue analysis at 650 °C is performed in samples with a stress-concentration. The effect of shot-peening on the fatigue lifetime is studied using both modeling and measurements. Results are in good agreement in the investigated range of applied stresses. However, measurements show that residual stresses from shot peening are not always beneficial.

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“…This is precisely the aim of the present work: a previously developed and validated model is used to simulate complex thermal histories and hence to optimise heat treatments. The model has already been described in detail [8], but its main features may be reminded: it consists in a finite element resolution, using a commercial code (Comsol [9]), of the nucleation and growth differential equations of Myhr and Grong [10], to model ageing precipitation in nickel base superalloys with a low γ' volume fraction (typically less than 0.3). Indeed, on the one hand Myhr and Grong equations hold in the case of a classical nucleation and growth phenomenon, and on the other hand they are well suited for the case of well-separated precipitates, corresponding to the case of alloys with a low γ' volume fraction.…”

Section: Introductionmentioning

confidence: 99%

“…In the present case, the Thermo-Calc software [11] is used, in conjunction with the TTNI7 thermodynamic database for Ni-base superalloys [12]. The obtained relations have been described elsewhere [8]. Finally, the γ' volume fraction, V f , is calculated using:…”

Section: Introductionmentioning

confidence: 99%

“…It has been shown that, once adjusted to experiment for a given alloy, the model can be used to simulate specific isothermal or non-isothermal ageing features, such as Temperature-Time-Transformation (TTT) and Continuous-Cooling-Transformation (CCT) curves, as well as a full heat-treatment [8]. The aim of the present work is to show how such a model can be used to optimise heat treatment following automated numerical routines.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Finite Element Simulation and Optimisation of Ageing Precipitation in Nickel Base Superalloys with a Low Gamma-Prime (g’) Volume Fraction

Tancret

Guillemet

Chabert

et al. 2011

SSP

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A finite element approach is used to simulate the precipitation of Ni3(Al,Ti) intermetallics in nickel-based superalloys containing a low volume fraction of spherical g’ precipitates, in which precipitation occurs following nucleation and growth mechanisms. Classical differential equations of nucleation and growth are implemented in the software Comsol (formerly Femlab), to compute the number of precipitates per unit volume and their mean size. Another originality of the model is the use of thermodynamic quantities coming from phase diagram computations (Thermo-Calc), like the temperature variation of the equilibrium g’ volume fraction, and the evolution of the concentration of g’ forming elements (Al, Ti) in the matrix with the volume fraction of precipitates. Once adjusted to experiment in the case of isothermal ageings, the model can be used to simulate precipitation during complex thermal histories. Finally, automatic heat treatment optimisation procedures are proposed and tested, which can reduce heat treatment times by a factor of more than five.

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Finite element simulation of interfacial segregation in dilute alloys

Cited by 12 publications

References 10 publications

Coupling Secondary Ion Mass Spectrometry and Atom Probe Tomography for Atomic Diffusion and Segregation Measurements

Coupling Secondary Ion Mass Spectrometry and Atom Probe Tomography for Atomic Diffusion and Segregation Measurements

Influence of Residual Stresses on the Fatigue Life of a Shot‐Peened Nickel‐Based Single Crystal Superalloy: From Measurements to Modeling

Finite Element Simulation and Optimisation of Ageing Precipitation in Nickel Base Superalloys with a Low Gamma-Prime (g’) Volume Fraction

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