Prediction of binary interaction coefficients in grain boundary segregation

The analysis of grain boundary (GB) diffusion in metallic systems based on Cu, Ni, Ag and Al was made to set demonstrate the common behavior. It was shown that the slow penetration for 11 systems can be connected with negative segregation or specific interatomic interaction. Two energetic parameters such as energy of interaction with GB and energy of interatomic interaction are proposed as main characteristics. The analysis of a tendency toward segregation and tendency of intermediate phase formation in these terms allows us to divide the systems on four groups and formulate a qualitative way to predict the behavior of the diffusing elements in a non-dilute solution. Mathematical formulation of GB diffusion problem and typical solutions are presented.

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“…That is the so-called Hondros and Seah’s rule [ 39 ]. More detailed analysis can be found, e.g., in [ 41 ].…”

Section: Resultsmentioning

confidence: 99%

The Algorithm to Predict the Grain Boundary Diffusion in Non-Dilute Metallic Systems

Tcherdyntsev

Rodin

2023

Materials

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“…Unfortunately, experimental data of the enthalpy of segregation are scarce and limited to few systems. In addition, their reliability strongly depends on the experimental procedure adopted and the system investigated [ 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 ] Therefore, it is not surprising that the attempts to relate theoretical predictions to experiments have been typically restricted to alloy systems whose experimental value of

is available or based on fitting procedure to estimate the unknown model parameters. Clearly, these approaches are limited by the availability of experimental information, and thus they cannot provide theoretical predictions of general applicability or be extended to unexplored systems.…”

Section: Introductionmentioning

confidence: 99%

Investigation on the Thermodynamic Stability of Nanocrystalline W-Based Alloys: A Combined Theoretical and Experimental Approach

et al. 2021

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The stability of nanostructured metal alloys is currently being extensively investigated, and several mathematical models have been developed to describe the thermodynamics of these systems. However, model capability in terms of thermal stability predictions strongly relies on grain boundary-related parameters that are difficult to measure or estimate accurately. To overcome this limitation, a novel theoretical approach is proposed and adopted in this work to identify W-based nanocrystalline alloys which are potentially able to show thermodynamic stability. A comparison between model outcomes and experimental findings is reported for two selected alloys, namely W-Ag and W-Al. Experimental results clearly highlight that W-Ag mixtures retain a segregated structure on relatively coarse length scales even after prolonged mechanical treatments. Moreover, annealing at moderate temperatures readily induces demixing of the constituent elements. In contrast, homogeneous nanostructured W-Al solid solutions are obtained by ball milling of elemental powders. These alloys show enhanced thermal stability with respect to pure W even at high homologous temperatures. Experimental evidences agree with model predictions for both the investigated systems.

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“…The limitation of these approaches is that they are derived from mean-field arguments. Even though there are some semi-empirical procedures to derive the meanfield interaction parameters [22], the mean-field model cannot always render the full complexity of the segregation and the connection with ab initio binding energies is not straightforward. There were some attempts to consider explicitly the short-range order in the first nearestneighbor shell [23] but this model is not easy to generalize to more complicated case.…”

Section: Introductionmentioning

confidence: 99%

Ab initio investigation of phosphorus and hydrogen co-segregation and embrittlement in α-Fe twin boundaries

Schuler

Christien

Ganster

et al. 2019

Applied Surface Science

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We propose a new statistical physics model to study equilibrium solute segregation at grain boundaries and the resulting embrittlement effect. This low-temperature expansion model is general and efficient, and its parameters can be obtained from atomistic calculations. It is possible to take into account multiple species, multiple segregation sites with different segregation free energies, account for configurational entropy, grain radius and site competition between solutes. As an example, the model is then applied to the study of phosphorus and hydrogen co-segregation at Σ3 109.5° 011 {111} twin boundaries in α-Fe, using energetic parameters from density-functional theory calculations. We show that P-H interactions may lead to increased P segregation at grain boundaries and cause additional embrittlement compared to the case where P and H are considered separately. cient statistics over a large number of GBs. Consequently, the study of GB segregation usually resorts to a combination of experimental techniques [7, 8] and results depend on the annealing temperature, bulk chemical composition, chemical environment and GB structure. The task becomes even more complicated when studying cosegregation effects, i.e. the simultaneous segregation of at least two chemical species which occurs all the time in real-life materials. There are several mechanisms at work: solute-GB interaction, solute-solute interaction at the GB and in the bulk, site competition, concentration ratio between solutes and kinetic properties of each solute [9]. For instance in Fe-P-C alloys, it was noted that intergranular P segregation decreases with increasing C content but the reason why this happens is not clear [8,10]. If Cr is added to this alloy it seems that P segregation increases only when C concentration is above a certain level [10].The pioneering work of Wu et al.[6] on Σ3[110](111) GB in α-Fe showed that ab initio methods were able to provide some insight on solute properties at GBs, as the authors were able to explain the strengthening by B additions and the embrittlement by P additions in terms of electronic structure at the GB and at free surfaces. These methods are fast-growing, and computation capabilities have increased a lot such that ab initio studies on GBs

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Prediction of binary interaction coefficients in grain boundary segregation

Cited by 6 publications

References 38 publications

The Algorithm to Predict the Grain Boundary Diffusion in Non-Dilute Metallic Systems

The Algorithm to Predict the Grain Boundary Diffusion in Non-Dilute Metallic Systems

Investigation on the Thermodynamic Stability of Nanocrystalline W-Based Alloys: A Combined Theoretical and Experimental Approach

Ab initio investigation of phosphorus and hydrogen co-segregation and embrittlement in α-Fe twin boundaries

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