On the third-generation Calphad databases: An updated description of Mn

The main focus in developing the third generation of CALPHAD databases is to model thermodynamic properties of materials by using models which are more physically based and valid down to 0 K. First‐principles calculations are helpful to choose and validate those models. Reliable calculation results, for example, at very low temperatures or on metastable systems reveal physical facts which might be inaccessible by experiments. Following our earlier work for modeling thermodynamic properties of pure elements (i.e., Fe and Mn) in third‐generation CALPHAD databases, the ε (hcp) phase was modeled as a metastable phase in the present work. Although hcp phase is just observed in these two elements under ultra‐high pressure, in the binary Fe–Mn this phase is metastable at ambient temperatures and pressures. Therefore, it should be properly modeled in unaries for later optimization of binary systems. Based on density functional theory (DFT) calculations, the magnetic ground state and the magnetic properties of ε‐Fe, ε‐Mn, and their binary solution phase were calculated. It was found that ε‐Fe is anti‐ferromagnetic (type II) while ε‐Mn has a paramagnetic ground state. Accordingly, magnetic contributions to thermodynamic properties were accurately modeled. Moreover, by means of the extrapolation of experimental data for the thermodynamic properties of binary systems and high‐pressure data for unaries, the metastable hcp phases at ambient pressure were modeled for the third‐generation CALPHAD database, consistently with other stable phases in the elements Fe and Mn.

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“…The lattice stability of hcp Mn compared to the stable allotropes from Ref. () is shown in Fig. and the heat capacity of hcp is presented in Fig.…”

Section: Calphad Approachmentioning

confidence: 99%

New description of metastable hcp phase for unaries Fe and Mn: Coupling between first-principles calculations and CALPHAD modeling

Bigdeli

Ehtehsami

Chen³

et al. 2016

Phys. Status Solidi B

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“…The most recent application of ChenSundman model (7) are the calculated Fe-C binary system [19] and the thermodynamic description of pure Mn [4].…”

Section: Chen-sundman Modelmentioning

confidence: 99%

“…The estimated parameter values with corresponding confidence intervals for the fitted SR are reported in Tab. 4.…”

Section: Pure Aluminum (Al)mentioning

confidence: 99%

Modeling of Gibbs energies of pure elements down to 0 K using segmented regression

Roslyakova

Sundman²,

Dette

et al. 2016

Calphad

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A novel thermodynamic modeling strategy of stable solid alloy phases is proposed based on segmented regression approach. The model considers several physical effects (e.g. electronic, vibrational etc.) and is valid from 0K up to the melting temperature. The preceding approach has been applied for several pure elements. Results show good agreement with experimental data at low and high temperatures. Since it is not a first attempt to propose a "universal" physical-based model down to 0K for the pure elements as an alternative to current SGTE description, we also compare the results to existing models. Analysis of the obtained results shows that the newly proposed model delivers more accurate description down to 0K for all studied pure elements according to several statistical tests.

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“…For the description of the liquid and amorphous phase Chen and Sundman adopted the so-called two-state model proposed by Ågren [25] where the liquid is assumed to consist of solid-like (amorphous-like, al ) and liquid-like ( ll ) atoms:

{}^{r e f}G_{m}^{L i q} = {}^{r e f}G_{m}^{a l} - R T \ln true[1 + \exp true(- \frac{Δ G_{d}}{R T} true) true],

where

Δ G_{d} = {}^{r e f}G_{m}^{l l} - {}^{r e f}G_{m}^{a l} = a + b t + c T \ln (T)

and

{}^{r e f}G_{m}^{l l}

and

{}^{r e f}G_{m}^{a l}

are the Gibbs energies of the liquid-like and amorphous-like states, respectively. These models have been applied to develop new descriptions of Fe [24] and Mn [26] and have been combined with conventional descriptions in the thermodynamic assessment of the Cr-Fe [27] system.…”

Section: Models and Gibbs Energy Minimizationmentioning

confidence: 99%

The Calphad Method and Its Role in Material and Process Development

Kattner¹

2016

TMM

115

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Successful design of materials and manufacturing processes requires the availability of reliable materials data. Commercial alloys usually contain a large number of elements, and the needed data for the design of new materials and processes are rarely available. The CALPHAD (CALculation of PHAse Diagrams) method enables the development of thermodynamic and property databases, that in conjunction with extrapolation methods of the descriptions of binary and ternary systems to higher-order systems, allow the calculation of data for higher-order systems. The results obtained from CALPHAD calculations have been shown to be invaluable in the design of new materials. This review presents an overview of the CALPHAD method, software tools and databases and gives examples of its application.

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On the third-generation Calphad databases: An updated description of Mn

Cited by 59 publications

References 100 publications

New description of metastable hcp phase for unaries Fe and Mn: Coupling between first-principles calculations and CALPHAD modeling

New description of metastable hcp phase for unaries Fe and Mn: Coupling between first-principles calculations and CALPHAD modeling

Modeling of Gibbs energies of pure elements down to 0 K using segmented regression

The Calphad Method and Its Role in Material and Process Development

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