First-principles study of an interfacial phase diagram in the V-doped WC-Co system

Johansson, Sven; Wahnström, Göran

doi:10.1103/physrevb.86.035403

Cited by 36 publications

(10 citation statements)

References 66 publications

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“…Engineers can use complexion diagrams, which present the complexion type for a given temperature and composition, to design a grain boundary with desirable properties . For example, a theoretical complexion diagram was calculated for a specific WC‐Co interface to identify the effect of temperature and V concentration on complexion type . The temperature that enabled the transformation of a submonolayer to monolayer complexion time was dependent on the global composition.…”

Section: Controlling Grain Boundariesmentioning

confidence: 99%

Review of grain boundary complexion engineering: Know your boundaries

et al. 2018

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Grain boundary structure-property relationships influence bulk performance and, therefore, are an important criterion in materials design. Materials scientists can generate different grain boundary structures by changes in temperature, pressure, and chemical potential because interfaces attain their own equilibrium states, known as complexions. Complexions undergo first-order transitions by changes in thermodynamic variables, which results in discontinuous changes in properties.Grain boundary complexion engineering is introduced in this paper as a method for controlling complexion transitions to improve material performance. This International Conference on Sintering 2017 lecture describes the tools for grain boundary complexion engineering: complexion equilibrium and time-temperaturetransformation (TTT) diagrams. These tools can be implemented in processing design to tailor grain boundary properties, including grain boundary mobility.While impactful, these diagrams are often limited in scope because they are currently empirically derived. This article discusses how measurement techniques can be combined with data analytical methods to build mechanistically derived complexion equilibrium and TTT diagrams.

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Section: Controlling Grain Boundariesmentioning

confidence: 99%

Review of grain boundary complexion engineering: Know your boundaries

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“…The CE coefficients are allowed to be different in the two different mixed layers. Monte Carlo (MC) simulations are then performed within the canonical ensemble and both the contribution to the temperature dependence of the energy (enthalpy) and entropy are determined [10].…”

Section: Temperature Dependent Partmentioning

confidence: 99%

“…For the interface energies presented in Tabs 1 and 2, the modeled interface orientation is the same as in Ref. [10]. For the carbide/Co calculations, we use metal-terminated carbide slabs containing 5 M + 4 C atomic (111) (for cubic MC) or (0001) (for WC) layers each with 3 atoms.…”

Section: Appendix a Computational Detailsmentioning

confidence: 99%

“…It has been well established that the appearance of certain interfacial "phases" different from those of the adjoining bulk phases (e. g. segregation structures, amorphous wetting films, etc.) can be understood from thermodynamic considerations [2,3,4,5,6,7,8,9,10,11,12,13,14,15]; the disparate interfacial phases are equilibrium states stabilized by the interface. The term complexion has been suggested to separate these interfacial phases from ordinary bulk phases [16,17,18].…”

Section: Introductionmentioning

confidence: 99%

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First-principles derived complexion diagrams for phase boundaries in doped cemented carbides

Johansson

Wahnström

2016

Current Opinion in Solid State and Materials Science

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This article reviews a method for calculating an equilibrium interfacial phase diagram depicting regions of stability for different interface structures as function of temperature and chemical potentials. Density functional theory (DFT) is used for interfacial energies, Monte Carlo simulations together with cluster expansions based on DFT results for obtaining configurational free energies, and CALPHAD-type modeling for describing the thermodynamic properties of the adjoining bulk phases. An explicit case, vanadium doped cemented carbides, is chosen to illustrate the progress in the research field and the interfacial diagram, a complexion diagram, for the phase boundary WC(0001)/Co is constructed as function of temperature and chemical potentials.

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“…The interaction between Co-based binders with different carbon contents and WC grains on early stages of liquid-phase sintering is thought to affect the well-known phenomenon of segregation of different grain growth inhibitors (vanadium carbide, chromium carbide, etc.) at WC/Co interfaces in cemented carbides [ 4 , 5 , 6 ]. Also, the interaction between Co-based binders and WC can lead to the formation of complexions in straight WC-Co cemented carbides that are not containing grain growth inhibitors [ 7 ].…”

Section: Introductionmentioning

confidence: 99%

Interfaces between Model Co-W-C Alloys with Various Carbon Contents and Tungsten Carbide

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Interfaces between alloys simulating binders in WC-Co cemented carbides and tungsten carbide were examined on the micro-, nano-, and atomic-scale. The precipitation of fine WC grains and η-phase occurs at the interface of the alloy with the low carbon content. The precipitation of such grains almost does not occur in the alloy with the medium-low carbon content and does not take place in the alloy with the high carbon content. The formation of Co nanoparticles in the binder alloy with the medium-low carbon content was established. Interfaces in the alloy with the medium-low carbon content characterized by complete wetting with respect to WC and with the high carbon content characterized by incomplete wetting were examined at an atomic scale. The absence of any additional phases or carbon segregations at both of the interfaces was established. Thus, the phenomenon of incomplete wetting of WC by liquid binders with high carbon contents is presumably related to special features of the Co-based binder alloys oversaturated with carbon at sintering temperatures.

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First-principles study of an interfacial phase diagram in the V-doped WC-Co system

Cited by 36 publications

References 66 publications

Review of grain boundary complexion engineering: Know your boundaries

Review of grain boundary complexion engineering: Know your boundaries

First-principles derived complexion diagrams for phase boundaries in doped cemented carbides

Interfaces between Model Co-W-C Alloys with Various Carbon Contents and Tungsten Carbide

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