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  Subjects -> ENGINEERING (Total: 2272 journals)
    - CHEMICAL ENGINEERING (190 journals)
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ENGINEERING (1204 journals)                  1 2 3 4 5 6 7 | Last

Showing 1 - 200 of 1205 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 7)
3D Research     Hybrid Journal   (Followers: 17)
AAPG Bulletin     Hybrid Journal   (Followers: 7)
AASRI Procedia     Open Access   (Followers: 15)
Abstract and Applied Analysis     Open Access   (Followers: 3)
Aceh International Journal of Science and Technology     Open Access   (Followers: 2)
ACS Nano     Full-text available via subscription   (Followers: 245)
Acta Geotechnica     Hybrid Journal   (Followers: 7)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 2)
Acta Scientiarum. Technology     Open Access   (Followers: 3)
Acta Universitatis Cibiniensis. Technical Series     Open Access  
Active and Passive Electronic Components     Open Access   (Followers: 7)
Adaptive Behavior     Hybrid Journal   (Followers: 11)
Adıyaman Üniversitesi Mühendislik Bilimleri Dergisi     Open Access  
Adsorption     Hybrid Journal   (Followers: 4)
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Advances in Remote Sensing     Open Access   (Followers: 37)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Aerobiologia     Hybrid Journal   (Followers: 1)
African Journal of Science, Technology, Innovation and Development     Hybrid Journal   (Followers: 4)
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Akademik Platform Mühendislik ve Fen Bilimleri Dergisi     Open Access  
Alexandria Engineering Journal     Open Access   (Followers: 1)
AMB Express     Open Access   (Followers: 1)
American Journal of Applied Sciences     Open Access   (Followers: 28)
American Journal of Engineering and Applied Sciences     Open Access   (Followers: 11)
American Journal of Engineering Education     Open Access   (Followers: 9)
American Journal of Environmental Engineering     Open Access   (Followers: 17)
American Journal of Industrial and Business Management     Open Access   (Followers: 23)
Analele Universitatii Ovidius Constanta - Seria Chimie     Open Access  
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Annals of Pure and Applied Logic     Open Access   (Followers: 2)
Annals of Regional Science     Hybrid Journal   (Followers: 7)
Annals of Science     Hybrid Journal   (Followers: 7)
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applicable Analysis: An International Journal     Hybrid Journal   (Followers: 1)
Applied Catalysis A: General     Hybrid Journal   (Followers: 6)
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Applied Clay Science     Hybrid Journal   (Followers: 5)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 12)
Applied Magnetic Resonance     Hybrid Journal   (Followers: 4)
Applied Nanoscience     Open Access   (Followers: 8)
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Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 4)
Arabian Journal for Science and Engineering     Hybrid Journal   (Followers: 5)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 4)
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Archives of Thermodynamics     Open Access   (Followers: 7)
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Asian Engineering Review     Open Access  
Asian Journal of Applied Science and Engineering     Open Access   (Followers: 1)
Asian Journal of Applied Sciences     Open Access   (Followers: 2)
Asian Journal of Biotechnology     Open Access   (Followers: 8)
Asian Journal of Control     Hybrid Journal  
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Asian Journal of Technology Innovation     Hybrid Journal   (Followers: 8)
Assembly Automation     Hybrid Journal   (Followers: 2)
at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
ATZagenda     Hybrid Journal  
ATZextra worldwide     Hybrid Journal  
Australasian Physical & Engineering Sciences in Medicine     Hybrid Journal   (Followers: 1)
Australian Journal of Multi-Disciplinary Engineering     Full-text available via subscription   (Followers: 2)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 8)
Avances en Ciencias e Ingeniería     Open Access  
Balkan Region Conference on Engineering and Business Education     Open Access   (Followers: 1)
Bangladesh Journal of Scientific and Industrial Research     Open Access  
Basin Research     Hybrid Journal   (Followers: 5)
Batteries     Open Access   (Followers: 5)
Bautechnik     Hybrid Journal   (Followers: 1)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 23)
Beni-Suef University Journal of Basic and Applied Sciences     Open Access   (Followers: 4)
BER : Manufacturing Survey : Full Survey     Full-text available via subscription   (Followers: 2)
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Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access   (Followers: 1)
Biofuels Engineering     Open Access  
Biointerphases     Open Access   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 10)
Biomedical Engineering     Hybrid Journal   (Followers: 16)
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Biomedical Engineering Letters     Hybrid Journal   (Followers: 5)
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Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 5)
Biomedical Microdevices     Hybrid Journal   (Followers: 9)
Biomedical Science and Engineering     Open Access   (Followers: 4)
Biomedizinische Technik - Biomedical Engineering     Hybrid Journal  
Biomicrofluidics     Open Access   (Followers: 4)
BioNanoMaterials     Hybrid Journal   (Followers: 2)
Biotechnology Progress     Hybrid Journal   (Followers: 39)
Boletin Cientifico Tecnico INIMET     Open Access  
Botswana Journal of Technology     Full-text available via subscription   (Followers: 1)
Boundary Value Problems     Open Access   (Followers: 1)
Brazilian Journal of Science and Technology     Open Access   (Followers: 2)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 10)
Bulletin of Canadian Petroleum Geology     Full-text available via subscription   (Followers: 14)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 9)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers, Droit, Sciences et Technologies     Open Access  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Hybrid Journal   (Followers: 22)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 43)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 8)
Case Studies in Thermal Engineering     Open Access   (Followers: 4)
Catalysis Communications     Hybrid Journal   (Followers: 6)
Catalysis Letters     Hybrid Journal   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 7)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysis Today     Hybrid Journal   (Followers: 8)
CEAS Space Journal     Hybrid Journal  
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 3)
Central European Journal of Engineering     Hybrid Journal   (Followers: 1)
CFD Letters     Open Access   (Followers: 6)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 2)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
Chinese Journal of Engineering     Open Access   (Followers: 2)
Chinese Science Bulletin     Open Access   (Followers: 1)
Ciencia e Ingenieria Neogranadina     Open Access  
Ciencia en su PC     Open Access   (Followers: 1)
Ciencias Holguin     Open Access   (Followers: 1)
CienciaUAT     Open Access  
Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Full-text available via subscription   (Followers: 11)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 14)
City, Culture and Society     Hybrid Journal   (Followers: 22)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
Coal Science and Technology     Full-text available via subscription   (Followers: 3)
Coastal Engineering     Hybrid Journal   (Followers: 11)
Coastal Engineering Journal     Hybrid Journal   (Followers: 5)
Coatings     Open Access   (Followers: 4)
Cogent Engineering     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Color Research & Application     Hybrid Journal   (Followers: 1)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 13)
Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 13)
Communications Engineer     Hybrid Journal   (Followers: 1)
Communications in Numerical Methods in Engineering     Hybrid Journal   (Followers: 2)
Components, Packaging and Manufacturing Technology, IEEE Transactions on     Hybrid Journal   (Followers: 26)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Composite Structures     Hybrid Journal   (Followers: 267)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 186)
Composites Part B : Engineering     Hybrid Journal   (Followers: 283)
Composites Science and Technology     Hybrid Journal   (Followers: 179)
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Concurrent Engineering     Hybrid Journal   (Followers: 3)
Continuum Mechanics and Thermodynamics     Hybrid Journal   (Followers: 7)
Control and Dynamic Systems     Full-text available via subscription   (Followers: 9)
Control Engineering Practice     Hybrid Journal   (Followers: 42)
Control Theory and Informatics     Open Access   (Followers: 8)
Corrosion Science     Hybrid Journal   (Followers: 25)
CT&F Ciencia, Tecnologia y Futuro     Open Access  
CTheory     Open Access  

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Journal Cover Calphad
  [SJR: 1.116]   [H-I: 44]   [0 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0364-5916
   Published by Elsevier Homepage  [3051 journals]
  • Reconciling SGTE and ab initio enthalpies of the elements
    • Abstract: Publication date: March 2018
      Source:Calphad, Volume 60
      Author(s): Axel van de Walle
      The CALPHAD framework is built on assumption that all phases have a well-defined free energy over all accessible composition, temperature and pressure conditions. Unfortunately, it is common for phases to exhibit mechanical instabilities in at least some range of conditions, thus precluding direct experimental measurements and hindering computational efforts. A pragmatic solution has often been to extrapolate free energies from stable region into the unstable regions, but extrapolations from different systems that share a common phase may not agree and extrapolated free energies can unintentionally lie below the free energy of stable phases. Computational approaches that aim to directly calculate the free energy of unstable phases offer a promising avenue to address these issues. Among them, the recently proposed “inflection detection” scheme lies on a strong theoretical footing. We provide further support for this approach by demonstrating that it yield free energies that agree very well with the widely used SGTE (Scientific Group Thermodata Europe) data for pure elements. This finding suggest that it may be possible to get the best of both worlds: obtain a theoretically justified definition of the free energy of mechanically unstable phases and preserve much of existing empirical standards for the assignments of such free energies.
      Graphical abstract image Highlights fx1

      PubDate: 2017-11-16T10:46:39Z
       
  • Density functional study of the thermodynamic properties and phase diagram
           of the magnesium hydride
    • Abstract: Publication date: March 2018
      Source:Calphad, Volume 60
      Author(s): Hasan S. AlMatrouk, Viorel Chihaia, Valentin Alexiev
      This paper focuses primarily on the P-T phase diagram determination by considering six polymorphs of magnesium hydride (α - rutile TiO2, P4 2 /mnm, β - cubic modified CaF2, Pa 3 ¯ , γ - orthorhombic PbO2, Pbcn, δ' - orthorhombic, Pbca and cubic - Fm 3 ¯ m). The Gibbs free energy and other thermodynamic properties were evaluated by DFT-based thermodynamic calculations, within the frame of the quasi-harmonic approximation, for the pressure range 0–10GPa and temperatures between 0 and 1200K. Furthermore, the structural, energetic, and electronic properties of the investigated structures are conversed.

      PubDate: 2017-11-16T10:46:39Z
       
  • Thermodynamic modeling of the V-Si-B system
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Antonio Augusto Araujo Pinto da Silva, Nabil Chaia, Flavio Ferreira, Gilberto Carvalho Coelho, Jean-Marc Fiorani, Nicolas David, Michel Vilasi, Carlos Angelo Nunes
      In the present work, the V-Si-B ternary system was thermodynamically modeled using the CALPHAD method. The thermodynamic descriptions of the V-Si and B-Si binary systems were taken from literature while the parameters of binary V-B were re-evaluated, based on new experimental information. The ternary thermodynamic description was based on experimental data of isothermal section and liquidus projection. The binary compounds V3B2, VB, V5B6, V3B4, V2B3 and VB2 were modeled as stoichiometric phases; the terminal solid solutions BCC and β-Rhomb were modeled using the sublattice models (V,Si)1(B,va)3 and (B)93(B, Si)12; the ternary phases D88 and T2 were modeled as (V)0.5556(B,Si)0.3333(B,va)0.1111 and (V)0.625(B,Si)0.375, respectively. A set of thermodynamic parameters is proposed and the results showed a good agreement with available experimental information from the literature.

      PubDate: 2017-11-09T09:20:00Z
       
  • First-principles calculations and thermodynamic modeling of the Yb-Ni
           binary system
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Yong-Jie Hu, Yi Wang, Samad A. Firdosy, Kurt E. Star, Jean-Pierre Fleurial, Vilupanur A. Ravi, Zi-Kui Liu
      A complete thermodynamic description of the Yb-Ni binary system is developed by means of the CALculation of PHAse Diagram (CALPHAD) method in combination with first-principles calculations based on density functional theory (DFT) and available experimental data in the literature. Finite temperature thermodynamic properties of the Yb-Ni intermetallic compounds are predicted using the quasi-harmonic approach, where first-principles phonon calculations are performed to calculate the lattice vibrational entropy. The associate solution model is used to describe the complex thermodynamic behavior of the liquid phase. The calculated phase diagram agrees well the experimental phase equilibrium data in the literature. By the coupling of CALPHAD modeling with first-principles calculations, the present work provides a more thermodynamically accurate model of the Yb-Ni system when compared to previous models.

      PubDate: 2017-11-09T09:20:00Z
       
  • Thermodynamic re-assessment of the Fe-Dy and Fe-Tb binary systems
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): M.H. Rong, X.L. Chen, J. Wang, G.H. Rao, H.Y. Zhou
      In this work, based on the critical evaluation of previous optimizations and available experimental data in the published literature, the Fe-Dy and Fe-Tb binary systems were re-assessed thermodynamically using the CALPHAD method. The solution phases including liquid, fcc-Fe, bcc-Fe, bcc-Dy, bcc-Tb, hcp-Dy and hcp-Tb, were described by the substitutional solution model and their excess Gibbs energies were expressed with the Redlich-Kister polynomial. Due to their narrow homogeneity ranges, the intermetallic compounds, Fe17Dy2, Fe23Dy6, Fe3Dy, Fe2Dy, Fe17Tb2, Fe23Tb6, Fe3Tb and Fe2Tb, were modeled as stoichiometric compounds. Self-consistent thermodynamic parameters to describe the Gibbs energies of various phases in the Fe-Dy and Fe-Tb binary systems were obtained finally. The calculated results are in good agreement with the reported phase equilibria and thermodynamic properties.

      PubDate: 2017-11-02T09:09:19Z
       
  • Numerical modelling of moving interfaces under local equilibrium
           conditions
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Jae Sang Lee, Dong-Woo Suh, Yang Mo Koo, Seong Gyoon Kim
      A new method is presented to simulate moving interfaces during diffusion-controlled growth under local equilibrium conditions. The position and compositions of the interface are obtained directly from the equilibrium state of the subsystem around the moving interface, without iterative calculation between diffusion fluxes and solute balance conditions. The method is applicable to general multi-component systems, and it ensures the consistency in compositions and solute balance at the interfaces; Those are ascribed to the presented consideration of subsystem around the interface region in a discretized form. Explicit equations of interface compositions and position in discretized variables are also presented for the simplified ternary systems of two-solution and compound/solution. The validity and usefulness of the method is demonstrated by simulations of the two important ternary systems; The simulation results illustrate the features of diffusion-controlled growth with different alloy compositions and diffusivities of solutes in both systems.
      Graphical abstract image

      PubDate: 2017-11-02T09:09:19Z
       
  • Thermodynamic modeling of phase equilibria and defect chemistry in the
           Zn-S system
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Pin-Wen Guan, Shun-Li Shang, Greta Lindwall, Tim Anderson, Zi-Kui Liu
      Though important and fundamental, a satisfactory theoretical framework of modeling multiple point defects in the context of phase equilibria is still lacking. In this work, a methodology that models point defects, electrons, holes and the underlying phase equilibria simultaneously is developed and applied to the Zn-S system. It overcomes some issues in previous works, such as inconsistency in the reference state for electrons. The model parameters are directly related to the Gibbs energy of formation of point defects computed from first-principles phonon calculations. A double exponential function is proposed to parameterize the entropy of formation of point defects as a function of temperature. Using this approach, phase diagrams, concentrations of point defects and free carriers, the majority carrier, and defect-related properties exemplified by the electrical conductivity are obtained under various conditions, in agreement with experimental data. The present methodology provides a way to integrate first-principles calculations and experimental data into the CALPHAD model, enabling description of multi-component semiconductor systems.

      PubDate: 2017-11-02T09:09:19Z
       
  • Phase relations in the Cu-O-Al2O3-SiO2 system at 1150°C and
           1300°C in air
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Niko Hellstén, Pekka Taskinen
      Phase equilibria of the Cu-O-Al2O3-SiO2 system are important in the processing of copper aluminosilicate glasses, mullite ceramics and in non-ferrous metallurgy. We experimentally investigated the phase equilibria of this system at 1150°C and 1300°C in air atmosphere using equilibration and quenching method. Chemical compositions of the liquid and solid phases in the quenched samples were determined by Electron Probe Microanalysis (EPMA). Based on the results, we constructed an isothermal section containing the liquidus contours of various primary phases at 1300°C. Comparison of these results with previous experimental work confirms that oxygen pressure affects phase stability and composition of the liquidus in this system. The experimental liquidus determined in this work disagrees by up to 50wt% with the calculated values of MTDATA 6.0 software and Mtox database version 8.2. Concentration of ‘Cu2O′ in mullite ranged from 0.46wt% to 1.25wt%. The results of this work will enable improvement of thermodynamic descriptions for this system.

      PubDate: 2017-11-02T09:09:19Z
       
  • Experimental investigation and thermodynamic calculation of the B-Fe-Mo
           ternary system
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Xuemei Ou Yang, Fucheng Yin, Jingxian Hu, Manxiu Zhao, Ye Liu
      The phase relationship of the B-Fe-Mo ternary system has been investigated combining experimental results with thermodynamic modeling. The liquidus projection of the ternary system in the Fe-rich region was constructed by identifying primary crystallization phases in the as-cast alloys and determining liquid temperatures obtained from the DSC analyses. Eight different primary solidification regions were observed, and they are BCC, FCC, Mo2FeB2, Fe2B, FeB, σ, and R, respectively. And four invariant reactions were identified in the Fe-rich region. Thermodynamic optimization of the B-Fe-Mo ternary system was performed using CALPHAD approach based on the thermodynamic models of the three constitutional binary systems and the experimental results of the ternary system. A set of self-consistent thermodynamic parameters for the B-Fe-Mo system were obtained with reasonable agreement between the experimental and calculated results.

      PubDate: 2017-11-02T09:09:19Z
       
  • CALPHAD modeling of metastable phases and ternary compounds in Ti-Al-N
           system
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Yanhui Zhang, Peter Franke, Hans Jürgen Seifert
      The development and evaluation of thermodynamic databases for the Ti-Al-N system is important for a wide range of engineering alloys. In this work, we resorted to the integration of ab initio thermodynamics, experiments and CALPHAD modeling for a comprehensive understanding of the metastable and the ternary phases in Ti-Al-N system. The supersaturated solutions of (Ti,Al)N with both rocksalt and wurtzite structures were well described by using the sub-regular solution model. Thereby, the formation, the phase separation and the meta-solubility of TiAlN coatings were successfully elaborated by the metastable pseudo-binary TiN-AlN section and the PVD (physical vapor deposition) phase diagram. Moreover, a number of isothermal and isopleth sections were also calculated and compared with available experiments and previous thermodynamic assessments. For the first time the ternary compound of τ 3 was corrected as Ti 4 AlN 3 in our proposed database.

      PubDate: 2017-10-14T14:28:02Z
       
  • Thermodynamic re-assessment of the Al-Co-W system
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Peisheng Wang, Wei Xiong, Ursula R. Kattner, Carelyn E. Campbell, Eric A. Lass, Oleg Y. Kontsevoi, Gregory B. Olson
      The Al-Co-W system and its binary sub-systems Al-Co, Al-W and Co-W were critically reviewed. The thermodynamic description of the Al-Co-W system including all three binaries was developed considering thermodynamic and constitutional data of the systems. Results from density functional theory calculations were employed to improve reliability of the descriptions. The Gibbs energy for the thermal vacancy (GVa) in the BCC_A2 phase is discussed. The revised descriptions obtained for the Al-W and Co-W systems describe the thermodynamic and phase equilibrium data well and are free of undesired artefacts for temperatures below 6000K. The ordered γ’ phase of the Al-Co-W system is described as a metastable phase in the entire temperature range. The calculated Gibbs energy of the γ’ is only slightly above that of the equilibrium state, which indicates that there is good possibility of stabilizing the γ’ phase with the addition of γ’-stabilizing elements, such as Ti, Ta, Hf, Nb and Ni.

      PubDate: 2017-10-11T14:13:11Z
       
  • Second nearest-neighbor modified embedded-atom method interatomic
           potentials for the Pt-M (M = Al, Co, Cu, Mo, Ni, Ti, V) binary systems
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Jin-Soo Kim, Donghyuk Seol, Joonho Ji, Hyo-Sun Jang, Yongmin Kim, Byeong-Joo Lee
      Interatomic potentials for Pt-M (M = Al, Co, Cu, Mo, Ni, Ti, V) binary systems have been developed on the basis of the second nearest-neighbor modified embedded-atom method (2NN MEAM) formalism. The parameters of pure Mo have also been newly developed to solve a problem in the previous 2NN MEAM potential in which the sigma and α-Mn structures become more stable than the bcc structure. The potentials reproduce various materials properties of alloys (structural, thermodynamic and order-disorder transition temperature) in reasonable agreements with relevant experimental data and other calculations. The applicability of the developed potentials to atomistic investigations for the shape and atomic configuration of Pt bimetallic nanoparticles is demonstrated.

      PubDate: 2017-10-11T14:13:11Z
       
  • A new thermodynamic description of stable Cr-carbides for the third
           generation of thermodynamic database
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Zhou Li, Huahai Mao, Malin Selleby
      An updated thermodynamic description of the stable Cr-carbides was obtained by applying the same models as used for the elements within the 3rd generation of thermodynamic databases. The Einstein model was used and a scaling factor was introduced to take into account the coupling effect between the stoichiometry (C to Cr ratio) and the structure of the compound. Using this model we could accurately describe the thermodynamic properties of these stoichiometric compounds using available experimental heat capacity data. The new description is now more physically sound and results in a better agreement with the experimental heat capacity data.

      PubDate: 2017-10-03T13:00:11Z
       
  • Thermodynamic modeling of the Ta–Mo–C ternary system
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Cong Zhang, Haiqing Yin, Yong Du, Yafei Pan, Peng Deng
      The Ta–Mo–C system was assessed by means of the CALPHAD approach. All of the phase diagram and thermodynamic information available from the literature were critically reviewed. The liquid was modeled as substitutional solution phase, while the carbides including fcc-(Mo,Ta)C1-x , bcc-(Mo,Ta), hcp-(Mo,Ta)2C and η-MoC were described by using corresponding sublattice models. The ζ-Ta4C3-x was considered as a linear compound with carbon content fixed, while shp-MoC was treated to be a binary stoichiometric phase. There was no ternary compound reported in this system. The modeling of Ta–Mo–C ternary system covers the entire composition and temperature ranges, and a set of self-consistent thermodynamic parameters for the Ta–Mo–C system was systematically optimized. Comprehensive comparisons between the calculated and reported phase diagram and thermodynamic data show that the reliable information is satisfactorily accounted for by the present modeling. The liquidus projection and reaction scheme of the Ta–Mo–C system were also generated by using the present thermodynamic parameters.

      PubDate: 2017-09-26T12:20:07Z
       
  • Thermodynamic modeling of the Ca(NO3)2-MNO3 (M: alkali metal) systems
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Xiang Li, Kun Wang, Miao Shen, Zhu Wu, Leidong Xie
      This work presents a thermodynamic evaluation of the Ca(NO3)2-MNO3 (M: Li, Na, K, Rb, Cs) binary systems using the CALPHAD approach. The required Gibbs energy of liquid Ca(NO3)2 is missing in the literature and has been successfully evaluated in the present work with a fusion enthalpy of 23849Jmol−1. The substitutional solution model can thus be employed to describe the Ca(NO3)2-base liquid phase. All the intermediate compounds are treated to be stoichiometric and their Gibbs energies comply with the Neumann-Kopp rule. Empirical functions relating mixing enthalpies to ionic parameters are employed to predict the corresponding values of binary melts which are used as input data to assist in parameters optimization for the liquid phases. The final calculated results show good agreement with most of the experimental and predicted data.

      PubDate: 2017-09-19T14:40:54Z
       
  • Diffusivities and atomic mobilities for fcc Cu–Ni–Sn alloys
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Yuling Liu, Chong Chen, Dandan Liu, Yong Du, Shuhong Liu, Xiaoma Tao, Yifang Ouyang
      Utilizing five groups of bulk diffusion couples together with electron probe microanalysis technique, the composition-dependent ternary interdiffusion coefficients in fcc Cu–Ni–Sn alloys at 1023K were determined via the Whittle and Green method. The presently obtained interdiffusion coefficients at 1023K as well as our previously measured ones at 1073K were combined with the slightly modified thermodynamic descriptions of the fcc Cu–Ni–Sn phase to explore atomic mobilities of Cu, Ni and Sn in fcc Cu–Ni–Sn alloys within the CALPHAD framework. In order to be consistent with the thermodynamic description, atomic mobilities in binary fcc Ni–Sn alloys were re-evaluated in the present work. The quality of the assessed kinetic characteristics was confirmed by the comprehensive comparisons between various model-predicted diffusion behaviors and the experimental ones, including concentration profiles and diffusion paths.

      PubDate: 2017-09-14T08:18:29Z
       
  • Ab initio-assisted assessment of the CaO-SiO2 system under pressure
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): D. Belmonte, G. Ottonello, M. Vetuschi Zuccolini
      We present the results of an ab initio-assisted assessment of melting and subsolidus phase relations in the system CaO-SiO2 up to high pressure conditions. All solid compounds known to nucleate in the system have been treated as purely stoichiometric and the liquid resolved in the framework of a simple polymeric model. Mixing properties of the binary liquid phase are fully described by a single-parameter purely enthalpic chemical interaction plus a strain energy contribution. The latter is required to predict liquid immiscibility of SiO2-rich liquid compositions at ambient conditions and becomes irrelevant at P>2GPa. A detailed survey of thermodynamic properties of silica polymorphs and calcium oxide and silicates in a broad range of P-T conditions reveals quite controversial stability relations and melting behavior. First-principles calculations on CaO and SiO2 pure liquid components and solid phases (lime and stishovite) have been used, along with a sound assessment of first- and second-order phase transitions, to reconcile thermochemical data with topological details of the observed phase diagrams. A physically-consistent coupling between thermodynamic and thermoelastic properties (viz. compressibility and thermal expansion) turns out to be of fundamental importance to infer reliable stability relations both at subsolidus and melting conditions. Pressure effects shift the composition of the main invariant points in the CaO-SiO2 system and also change the melting behavior of the CaSiO3 metasilicate in a complex manner.

      PubDate: 2017-09-02T07:41:30Z
       
  • Phase equilibria in the ternary Fe-Co-S system
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Mariia O. Ilatovskaia, Svetlana I. Sinyova, Roman V. Starykh
      The Fe-FeS-CoS-Co system has been investigated experimentally from 1073K up to liquidus temperature. Samples of the system have been investigated using DTA/TGA, SEM/EDX, and XRD methods. Liquidus and solidus projections have been plotted based on experimental data.

      PubDate: 2017-09-02T07:41:30Z
       
  • Vapor pressure of alkali-metal binary alloys in glass cells
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Kiyoshi Ishikawa
      The alkali partial pressures of composite alkali-metal vapor are crucial in atomic-physics optical experiments. The vapor pressures of alkali-metal binary alloys can be calculated by using the activity and the mixing enthalpy for homogeneous alloys from early measurements. We show that the results of sodium-containing alloys deviate appreciably from the prediction of Raoult's law. Experimentally, the phase and the mixing ratio of binary alloys are non-destructively measured by nuclear-magnetic-resonance spectroscopy in glass cells. We find that many droplets of the sodium-rubidium alloy exist on the cell walls, and they have different mixing ratios. Therefore, the vapor density varies microscopically around the glass cells. To achieve precision optical measurements, we should take account of the pressure change due to the equilibrium process and further sodium contamination over the lifetime of glass cells.

      PubDate: 2017-09-02T07:41:30Z
       
  • The reassessment of the Al-V system and new assessment of the Al-Si-V
           system
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): A. Kroupa, M. Mazalová, K.W. Richter
      The theoretical assessment of the Al-Si-V system has been carried out and has been presented here. The experimental results from Huber et al. [1,2] were used as the basis of the assessment. The relevant binary system assessments for Al-V [9], Al-Si [13] and Si-V [14] were used in the initial stage of the study and it was found that complete reassessment of the Al-V system was necessary. The reassessed dataset for the Al-V system is in very good agreement not only with existing experimental phase diagram and thermodynamic data, but is also consistent with the independent work of Lindahl et al. [22]. The final assessment of the Al-Si-V system using our own reassessed Al-V system is in excellent agreement with the experimental data.

      PubDate: 2017-09-02T07:41:30Z
       
  • Thermodynamic reassessment of the novel solid-state thermal energy storage
           materials: Ternary polyalcohol and amine system
           pentaglycerine-tris(hydroxymethyl)-amino-methane-neopentylglycol
           (PG-TRIS-NPG)
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Renhai Shi, Dhanesh Chandra, Amrita Mishra, Anjali Talekar, Muralidhar Tirumala, Daryl J. Nelson
      Organic polyalcohol and amine globular molecular crystals such as PG, TRIS, and NPG are considered as the most promising potential candidates for solid-state thermal energy storage in the orientationally disordered high temperature phases. In this study, we first propose a new PG-TRIS-NPG phase diagram based on experimental data of the three sub-binary systems NPG-PG, PG-TRIS, and NPG-TRIS with CALPHAD methodology. The NPG-PG binary phase diagram was optimized using sub-regular models that showed complete miscibility in the entire compositional range of high temperature γ′ (FCC) phase region, and an invariant equilibrium point at 299.5K. The NPG-TRIS binary system was also calculated using sub-regular model, from sub-ambient to well above the melting temperatures, and determined three invariant equilibria at 311.1K, 391.8K, and 410.6K, respectively. These calculated binary phase diagrams are in good agreement with the experimental data. The PG-TRIS-NPG ternary system has also been calculated and qualitatively analyzed using the CALPHAD method and Thermo-Calc software. A set of self-consistent thermodynamic parameters formulating the Gibbs energies of various phase in the PG-TIRS-NPG ternary system are obtained in the present work. Thermodynamic properties such as several isotherms, isopleths, and liquidus projections are calculated by using present datasets as shown in this work in which the solid ternary compound (TRIS0.5NPG0.5)XPG1−X (0.1≤x≤0.9), (TRIS0.5PG0.5)XNPG1−X (0.1≤x≤0.9), and (PG0.5NPG0.5)XTRIS1−X (0.1≤x≤0.9) with various solid-solid phase transitions at different temperatures could apply to applications in the solid-state thermal energy storage.

      PubDate: 2017-09-02T07:41:30Z
       
  • A method of integrating CALPHAD data into phase-field models using an
           approximated minimiser applied to intermetallic layer growth in the Al-Mg
           system
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): M.J. Welland, M.H.A. Piro, S. Hibbins, N. Wang
      This article describes an approach to combine single phase thermodynamic potentials into a multiphase composite potential suitable for integration in a multicomponent phase-field model. The composite potential avoids implicit interfacial energy contributions by starting from a grand potential formulation. The method is made explicit by expanding the minimiser resulting from the Legendre transform between grand and Helmholtz potentials about a known equilibrium state. The resulting composite function is explicit, reproduces the equilibrium states exactly, and is smooth such that it can be differentiated to provide the driving forces for mass transport and phase change in a thermodynamically self-consistent manner. The model is demonstrated by simulating a sequence of phase transformations for intermetallic growth in Al-Mg interdiffusion for advanced nuclear research reactor fuel.

      PubDate: 2017-09-02T07:41:30Z
       
  • Critical assessment and thermodynamic modeling of the
           Cu–Fe–O–Si system
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): Taufiq Hidayat, Denis Shishin, Sergei A. Decterov, Evgueni Jak
      The present study is the first Calphad-type assessment of the Cu–Fe–O–Si system. All relevant thermodynamic and phase equilibrium data have been critically evaluated to produce a thermodynamic database describing the Gibbs energies of all phases in the system. The predictive range of the database covers all conditions of pyrometallurgical production of copper in terms of temperature and oxygen partial pressure. Liquid oxide slag and liquid metal phases have been described using two separate solution models, both developed within the framework of the Modified Quasichemical Formalism. Slag model is expressed as [Cu+, Fe2+, Fe3+, Si4+][O2-] and metal model is expressed as (CuI, FeII, OII). They are internally consistent with the models for fcc–Cu, fcc–Fe, bcc–Fe, spinel, wüstite, CuFeO2, Cu2O, Fe2SiO4, Fe2O3 and SiO2 obtained in the previous optimizations of the Cu–O, Fe–O, Cu–Fe, Cu–Fe–O, Cu–O–Si, Fe–O–Si sub-systems.

      PubDate: 2017-09-02T07:41:30Z
       
  • Critical evaluation of thermodynamic properties of rare earth sesquioxides
           (RE = La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc and
           Y)
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): Yumin Zhang, In-Ho Jung
      In order to develop the thermodynamic database containing rare earth sesquioxides (RE2O3), accurate thermodynamic descriptions of all stable and metastable RE2O3 phases are required. Rare earth sesquioxides have five polymorphs, which are (from low to high temperature) the cubic phase (C), the monoclinic phase (B), the hexagonal phase (A), the high temperature hexagonal phase (H), and the high temperature cubic phase (X). However, the thermodynamic property data of all polymorphs available in the literature are insufficient. In particular, the thermodynamic data for the phases stable only at high temperatures and for metastable phases are not well investigated. In this study, all ∆ H 298 K o , S 298 K o , C P (or heat content) and phase transition temperature (T tr ) data available in the literature for each rare earth sesquioxide were collected and critically evaluated based on the sample preparations, experimental procedures and characterization techniques. Relationships between ∆ H 298 K o , S 298 K o , and T tr against the ionic radii of the entire rare earth cations were then established and missing thermodynamic information was predicted based on the general trends. In these ways, the accurate and consistent Gibbs energies of all stable and metastable RE2O3 phases (RE = La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y and Sc) were prepared. These Gibbs energy data can be readily used for the development of a comprehensive thermodynamic database containing rare earth oxides.

      PubDate: 2017-09-02T07:41:30Z
       
  • Calorimetric measurement of the standard enthalpy of formation of ZnSb at
           298 K
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): P. Benigni, A. Berche, R. Pothin, A. Adenot, G. Mikaelian, R.M. Ayral, P. Jund, J. Rogez
      After a critical review of the literature data on the standard enthalpy of formation of ZnSb, discrepancies between various experimental studies are highlighted. Moreover, experimental values disagree with values calculated by ab initio methods. As many of the experimental methods used suffer from some serious drawbacks, a new determination of the standard enthalpy of formation of ZnSb by an alternative calorimetric method, drop solution calorimetry in liquid tin, has been performed. Two different synthesis methods have been used to obtain a pure ZnSb phase and drop solution experiments were performed at 665 and at 974K. The standard enthalpy of formation values derived from these experiments are − 6.1±2.5kJmol of atoms−1 for the ZnSb sample prepared by ball milling and − 7.9±0.4kJmol of atoms−1 for the ZnSb sample prepared by melting. These results are discussed and compared to literature data.

      PubDate: 2017-09-02T07:41:30Z
       
  • Experimental investigation and thermodynamic description of the Cu-Cr-Zr
           system
    • Abstract: Publication date: December 2017
      Source:Calphad, Volume 59
      Author(s): Yuling Liu, Peng Zhou, Shuhong Liu, Yong Du
      The Cu-Cr-Zr ternary system was investigated via thermodynamic modeling coupled with key experiments. The isothermal section of the Cu-Cr-Zr system at 1123K was determined by means of optical microscopy, X-ray diffraction and electron probe microanalysis, and the phase transformation temperatures were measured by differential scanning calorimetry. The Cu-Cr sub-binary system was re-assessed with a substitutional solution model for the solution phases to ensure its compatibility in multi-component system. A set of self-consistent thermodynamic parameters for the Cu-Cr-Zr systems was obtained using the CALPHAD (CALculation of PHAse Diagram) approach, and the calculated phase diagram is in a satisfactory agreement with the present experimental results and literature information. An increase of the thermodynamic stability for the CuZr and Cr2Zr phases due to the ternary solubility is verified by calculation.

      PubDate: 2017-08-03T11:16:57Z
       
  • Thermodynamic description of the Al–Ge–Ni system over the whole
           composition and temperature ranges
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): Chenyang Zhou, Jiaxin Cui, Cuiping Guo, Changrong Li, Zhenmin Du
      The phase equilibria and thermodynamic properties of the Al–Ge–Ni system are useful for understanding the diffusion process during the transient liquid phase (TLP) bonding. In this work, the thermodynamic description of the Al–Ge–Ni system over the whole composition and temperature ranges was performed by means of the CALPHAD (CALculation of PHAse Diagrams) method. The enthalpies of mixing of the liquid phase, three isothermal sections at 973, 823, and 673K and nine vertical sections at 10, 20, 35, 55, 60, 70, 75, and 80at% Ni and at a constant Al:Ni ratio of 1:3 were taken into account in the present optimization work. A set of self-consistent thermodynamic parameters of the Al–Ge–Ni system was first obtained. The liquidus projection and reaction scheme were constructed according to the thermodynamic parameters obtained in this work. The phase equilibria and thermodynamic properties calculated by the present thermodynamic description show satisfactory agreement with the available experimental information.

      PubDate: 2017-07-24T11:01:09Z
       
  • Thermodynamic re-assessment of the Fe-Gd and Fe-Sm binary systems
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): X.L. Chen, J. Wang, T.L. Chen, X.D. Lin, M.H. Rong, G.H. Rao, H.Y. Zhou
      The Fe-Gd and Fe-Sm binary systems were re-assessed thermodynamically using the CALPHAD method based on the critical evaluation of previous optimizations and available experimental information in the published literature. The solution phases including liquid, fcc-Fe, bcc-Fe, bcc-Gd, hcp-Gd, bcc-Sm, hcp-Sm and rhombohedral-Sm, were described by the substitutional solution model and their excess Gibbs energies were expressed with the Redlich-Kister polynomial. The intermetallic compounds, α-Fe17Gd2, β-Fe17Gd2, Fe23Gd6, Fe3Gd, Fe2Gd, Fe17Sm2, Fe3Sm and Fe2Sm, were modeled as stoichiometric compounds due to their narrow homogeneity ranges. Self-consistent thermodynamic parameters to describe Gibbs energies of various phases in the Fe-Gd and Fe-Sm binary systems were obtained finally. The calculated results in this work are in good agreement with the reported phase equilibria and thermodynamic properties.

      PubDate: 2017-07-24T11:01:09Z
       
  • Investigation of the phase equilibria in Ti-Ni-Hf system using diffusion
           triples and equilibrated alloys
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): J.L. Liu, L.L. Zhu, X.M. Huang, G.M. Cai, Z.P. Jin
      In present work, the phase equilibrium relations in the Ti-Ni-Hf ternary system, which are of great importance for the design of Ti-Ni based high temperature shape memory alloys, were investigated using diffusion triples and sixteen key equilibrated alloys. Based on the experimental results from electron-probe microscopy analysis (EPMA) and X-ray diffraction (XRD) techniques, two isothermal sections were constructed, which consist of 13 and 12 three-phase regions at 900°C and 800°C, respectively. Hf can substitute for Ti in TiNi and Ti2Ni phases increasing from 30, 62at% at 800°C to 36, 64at% at 900°C, respectively. The Hf7Ni10 and Hf9Ni11 phases show wide ternary composition ranges, while the solubility of Ti in HfNi5, Hf2Ni7, and HfNi phases are relatively limited. A new ternary phase of τ was detected for the first time, and the stoichiometry of τ phase is close to Ni:(Hf,Ti) = 11:14, with Ti substituting for Hf from ~5at% to ~22at%. The single-phase region of the τ phase became narrow as the decreasing of annealing temperature. Based on comparison of phase relations at 900°C and 800°C, it is speculated there is an invariant reaction TiNi + τ → HfNi + Ti2Ni at between 900°C and 800°C.
      Graphical abstract image

      PubDate: 2017-07-24T11:01:09Z
       
  • Experimental investigations and DICTRA® simulation of sigma phase
           formation in a duplex stainless steel
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): Luara da Costa Morais, Rodrigo Magnabosco
      Sigma phase formation in an UNS S31803 duplex stainless steel aged at 940°C was evaluated by computational simulation in DICTRA® software, using MOB2 diffusion database and TCFE8 thermodynamic database. Simulation results were compared to experimental tests. Two models were tested in DICTRA® software: in model 1 sigma phase are placed between ferrite and austenite, and in model 2 sigma is placed at one side of ferrite region, and austenite on the other. The volume fraction of sigma and ferrite phases obtained in model 1 showed adherence to the experimental results up to 7200s (2h) of simulation, indicating the ability of the model in the description of early stages of sigma formation. Model 2 showed good agreement with experimental data up to 86,400s (24h) of simulation. The composition profile obtained by the simulation of the model 1 represented better the impoverishment in Cr and Mo in ferrite/sigma and austenite/sigma interfaces, while the profiles obtained by the simulation of model 2 described better the partition of the chemical elements between austenite and ferrite during sigma formation.

      PubDate: 2017-07-24T11:01:09Z
       
  • Ti-17 volatilization under vacuum: Investigation of the activity
           coefficients at 1900°C
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): Colin Reimer, Julien Jourdan, Jean-Pierre Bellot
      Vacuum processing techniques are a valuable industrial tool for the processing of reactive metals and alloys. However, drawbacks caused by the selective volatilization of alloying elements lead to an hard prediction of final alloy composition. By understanding the behaviour of the alloying elements and the interactions between them, improved compositional accuracy can be achieved. The evaluation of the activity coefficients is a key property that relates partial vapor pressure with the Langmuir law to accurately predict the mass flux of the individual elements in an alloy. This study takes a look at the grade Ti-17 which exhibits a relative large number of alloying elements. By using an electron beam furnace and a vapor deposition apparatus the necessary measurements were made to evaluate activity coefficients for each of the volatizing elements in the alloys including Aluminum, Chromium, Tin. Comparisons were made between experiments and the findings suggest that the primary interactions between the alloying elements with titanium result in small deviations between alloys. The results for the experiments provided reliable and repeatable results.

      PubDate: 2017-07-12T10:01:11Z
       
  • Experimental investigation and thermodynamic assessment of the
           Mo–Ni–Zr ternary system
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): Shimin Wang, Cong Zhang, Yong Du, Yingbiao Peng, Yafei Pan, Peng Zhou, Liya Dreval
      The isothermal section of the Mo–Ni–Zr system at 1100°C was investigated by characterization of eight equilibrium alloys. X-ray diffraction (XRD) and electron probe microanalysis (EPMA) were used to identify the stable phases and obtain their compositions. The Mo–Ni–Zr system was then optimized by means of CALPHAD (CALculation of PHAse Diagrams) technique with the consideration of experimental data obtained in the present work and reported in the literature. The liquid, fcc, bcc and hcp solution phases, were modeled with (sub-)regular solution model. The compound Zr65Mo18−xNi16.5+x (τ1, cF96-Ti2Ni) was described as Zr2(Mo, Ni) based on its crystal structure and solubility range. While τ2 (Zr65Mo27.3Ni7.7) phase was modeled as a stoichiometric compound due to its limited homogeneity range. A set of self-consistent thermodynamic parameters for the Mo–Ni–Zr system was finally obtained. Comprehensive comparisons between the calculated and experimental phase diagram data show that the experimental information is satisfactorily accounted for by the present thermodynamic description. The liquidus projection and reaction scheme of the Mo–Ni–Zr system were also generated by using the present thermodynamic parameters.

      PubDate: 2017-07-12T10:01:11Z
       
  • Updating the estimated assemblage of stable phases in a Gibbs energy
           minimizer
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): M.H.A. Piro
      Several numerical strategies are presented that can be used to effectively and efficiently update the estimated assemblage of stable phases in a Gibbs energy minimizer. Decisions must be made in selecting which phase should be added to or withdrawn from the system, the order in which certain combinations should be considered, testing procedures of the appropriateness of a candidate system for further consideration, etc. The manner in which these methods are performed have a profound effect on the performance and reliability of such calculations; without effective strategies, the solution may not converge. While these matters are somewhat straightforward for relatively small systems, far greater challenges are experienced in large systems containing many chemical elements. These matters will be discussed and effective solutions that have been integrated into thermochimica throughout the course of its development will be presented.

      PubDate: 2017-07-03T09:07:26Z
       
  • Software tools for high-throughput CALPHAD from first-principles data
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): Axel van de Walle, Ruoshi Sun, Qi-Jun Hong, Sara Kadkhodaei
      We present a set of software tools that largely automate the process of converting ab initio data into thermodynamic databases that can readily be imported into standard thermodynamic modeling softwares. These tools are based on the Special Quasirandom Structures (SQS) formalism, extended to transparently handle, not only traditional fcc, bcc and hcp solid solutions, but also multiple-sublattice structures with possible sublattice disorder. A large database of pre-generated SQS is provided that covers over 30 of the most common multi-sublattice structures and spans the composition ranges of each of their sublattices. In addition, we exploit a theoretically justified and robust method to address the issue of assigning free energies to mechanically unstable “virtual” phases, thus providing a compelling solution to a long-standing problem in CALPHAD modeling, especially in the context of ab initio data. We also propose a simple low-order approximation scheme to include short-range order effects that requires no additional ab initio input. The resulting thermodyamic database seamlessly combines ab initio data (formation energies and, optionally, vibrational free energies) with elemental Scientific Group Thermodata Europe (SGTE) data. The proposed tools provide a clear path to expand the coverage of high-throughput efforts towards non-stoichiometric phases and non-zero temperatures. The generated free energy models can also provide very good starting points to perform complex thermodynamic assessments, especially in cases where the available experimental data poorly constrain some thermodynamic parameters. The Cu-Pt-W phase diagram is calculated as an example.
      Graphical abstract image Highlights fx1

      PubDate: 2017-06-12T07:40:52Z
       
  • Thermodynamic and diffusion kinetic studies of the Fe-Co system
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): Jingjing Wang, Xiao-Gang Lu, Naqiong Zhu, Weisen Zheng
      The phase equilibria, thermodynamic properties and diffusion mobilities of the Fe-Co system were carefully assessed through the CALPHAD methods. As an indispensable tool, the first-principles calculations were carried out to study the magnetic moments and the enthalpies of mixing of the bcc_A2, bcc_B2, fcc_A1 and hcp_A3 phases as well as the point defect types of the bcc_B2 phase. In order to verify the heat capacities reported in the literature, new measurements were conducted in a high-temperature calorimetric apparatus using the three-dimensional calorimetric method. Because of the revision of the thermodynamic parameters in the present work, the diffusion mobilities for the fcc_A1 phase were reassessed. The diffusion mobilities for the bcc_A2 phase were established for the first time based on the experimental diffusion coefficients. For the low-temperature bcc_B2 phase, the diffusion couple experiments conducted in the present work show that the diffusion process is sluggish and the interdiffusion coefficients are difficult to determine. Therefore the tracer diffusivities of Co and Fe in the Fe-Co alloys were used to assess the diffusion mobilities for the bcc_B2 phase, while the composition-distance profile of one diffusion couple was served as a validation of its diffusion mobilities.

      PubDate: 2017-06-12T07:40:52Z
       
  • Experimental investigation of phase equilibria in the Ti-Fe-Cr ternary
           system
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): Lijun Zeng, Libin Liu, Shuaixiong Huang, Ligang Zhang
      Phase equilibria in ternary Ti-Fe-Cr system at 873 and 1173K were investigated in this work. Based on the phase constitutions and phase compositions in 32 samples prepared using the equilibrated alloys, the isothermal sections of the Ti-Fe-Cr ternary system were established. For this system, there were six three-phase regions at both 873 and 1173K, the phase relations at the studied two temperatures are almost the same. Thereinto, two tentative three-phase regions of βCr2Ti + β(Ti) + (Fe, Cr)2Ti and βCr2Ti + β(Ti) + αCr2Ti were deduced near the Ti-Cr side at 1173K. The (Fe, Cr)2Ti phase has a large solubility of Cr, up to 59.1at% at 873K and 59.5at% at 1173K. Moreover, at 873 and 1173K, the homogeneity ranges of the nearly linear ternary compounds τ1 were measured to be 49.9–72.1at% Fe and 52.7–77.2at% Fe, respectively, and the solubility of Cr in (Fe, Cr)Ti were 9.0at% and 10.6at%.

      PubDate: 2017-06-07T03:28:43Z
       
  • Design of Laves-phase-packed spheres in wear-resistant Cu alloy by
           controlled liquid immiscibility
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): Kouji Tanaka, Hajime Kato, Tadashi Oshima
      The designed liquid immiscibility of Cu-Ni-Fe-Mo-Si alloy led to separation of the spherical second liquid in the Cu-rich liquid, which solidified into coarse hard grains packed with Laves phase. The coarseness of hard grains was controlled not only by the repulsive interactions in Cu–Fe and Cu–Mo system, but also the refining effect of Ni and Si. CALPHAD analysis of the multicomponent system confirmed the correlation of the calculated fraction of the separated liquid with the observed grain dimensions. It also provided a powerful prediction of the precipitates constituting the hard grains. Almost all of the alloying effects on the observed microstructures were successfully interpreted based on equilibrium immiscibility calculations, although a reason for the refining of spheres with increasing Si remains unclear.
      Graphical abstract image

      PubDate: 2017-05-27T12:33:54Z
       
  • Thermodynamic assessment of the Al-C-Fe system
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): Weisen Zheng, Shuang He, Malin Selleby, Yanlin He, Lin Li, Xiao-Gang Lu, John Ågren
      The Al-C-Fe system was assessed in the framework of the CALPHAD approach. Through the critical review of thermochemical properties of liquid Al-Fe alloys, the binary Al-Fe description was revised to agree better with the experimental data. The partitioning model based on the Compound Energy Formalism (CEF) was utilized to describe the disordered and ordered bcc, fcc and κ phases. Moreover, ab initio calculations were performed to determine the enthalpies of formation of the ordered structures based on the bcc and fcc lattices in the binary Al-Fe and for the end-members of the κ phase in the ternary Al-C-Fe system. In order to simplify the database, the present work also employed a two-sublattice model to describe the B2 ordered phase in the Al-Fe system, which can be applied easily to diffusion simulations. Comprehensive comparison between the model-predicted and experimental data confirms that the present evaluation describe the Al-C-Fe system satisfactorily, especially the κ phase.

      PubDate: 2017-05-18T11:47:04Z
       
  • Experimental and thermodynamic study of the Mg-Sn-Ca-Sr quaternary system:
           Part I-Mg-Sn-Ca ternary system
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): Jian Wang, Jiajian Han, Beining Du, Yixiong Huang, Liyuan Sheng, Weifeng Rao, Cuiping Wang, Xingjun Liu
      Four key samples of the Mg-Ca-Sn ternary system in the Mg-rich region at 415 and 350°C have been determined using the Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-Ray Spectrometry (EDS). The existence of the CaMgSn ternary compound was confirmed in these two isothermal sections. Thermodynamic optimizations of the Ca-Sn binary system and Mg-Ca-Sn ternary system were carried out using the CALPHAD (Calculation of Phase Diagrams) technique. The Modified Quasichemical Model (MQM) was used for the liquid solution which exhibits a high degree of short-range ordering behavior in the liquid solution. The solid phases are modeled with the Compound Energy Formalism (CEF). Finally, a self-consistent thermodynamic database of Mg-Ca-Sn ternary system has been constructed in the present work, which would provide an efficient and convenient way to study and develop the new Mg-Sn based alloys.

      PubDate: 2017-05-13T11:33:23Z
       
  • Thermodynamic modeling of the PbX (X=S,Te) phase diagram using a five
           sub-lattice and two sub-lattice model
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): M.C. Peters, Jeff.W. Doak, W.-W. Zhang, J.E. Saal, G.B. Olson, P.W. Voorhees
      Five-sublattice and two-sublattice models have been built to describe the PbX (X=S,Te) semiconductors using the CALPHAD method. The five-sublattice model has three additional sublattices to explicitly model interstitials, electrons, and holes. The experimental literature has been critically reviewed and many high temperature carrier concentration results used in previous assessments have been shown to be unreliable. First-principle calculations for the formation energies of neutral defects and their respective ionization energies have also been incorporated into the models. The models show an improvement over previous assessments of PbTe and are the first time PbS has not been treated as a stoichiometric compound in a CALPHAD assessment.

      PubDate: 2017-05-13T11:33:23Z
       
  • Au-Ni nanoparticles: Phase diagram prediction, synthesis,
           characterization, and thermal stability
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): J. Sopoušek, A. Kryštofová, M. Premović, O. Zobač, S. Polsterová, P. Brož, J. Buršík
      The Au-Ni nanoparticles (NPs) were prepared by oleylamine solvothermal synthesis from metal precursors. The Au-Ni phase diagram prediction respecting the particle size was calculated by the CALPHAD method. The hydrodynamic size of the AuNi NPs in a nonpolar organic solvent was measured by the dynamic light scattering (DLS) method. The average hydrodynamic sizes of the nanoparticle samples were between 18 and 25nm. The metallic composition of the AuNi NP samples was obtained by inductively-coupled plasma atomic emission spectroscopy (ICP-OES). The metallic fraction inside AuNi NPs was varied Au-(30–70)wt%Ni. The steric alkylamine stabilization was observed. The individual AuNi NPs were investigated by transmission electron microscopy (TEM). The dry nanopowder was also studied. The structures of the aggregated samples were investigated by scanning electron microscopy (SEM). The AuNi NPs reveal randomly mixed face-centered cubic (FCC) crystal lattices. The phase transformations were studied under inert gas and air. The samples were studied by differential scanning calorimetry (DSC).

      PubDate: 2017-05-13T11:33:23Z
       
  • Thermodynamic model for prediction of binary alloy nanoparticle phase
           diagram including size dependent surface tension effect
    • Abstract: Publication date: September 2017
      Source:Calphad, Volume 58
      Author(s): Fatemeh Monji, Mohammad Amin Jabbareh
      Considering the size effect of nanoparticles on surface tension, a new CALPHAD type thermodynamic model was developed to predict phase diagram of binary alloy nanoparticle systems. In contrast to conventional model, the new model can be applied to the nanoparticles smaller than the critical size (5NM in radius). For an example, the model applied to Ag – Au binary system and the results were compared with experimental data as well as conventional CALPHAD model and molecular dynamics simulation results.

      PubDate: 2017-05-02T10:41:32Z
       
  • Thermodynamic modelling of the Cr-Nb-Sn system
    • Abstract: Publication date: June 2017
      Source:Calphad, Volume 57
      Author(s): Paul Lafaye, Caroline Toffolon-Masclet, Jean-Claude Crivello, Jean-Marc Joubert
      The Cr-Nb-Sn system has been studied experimentally, by first principles calculation and finally modeled with the Calphad method. The experimental study has been carried out on the Cr-Sn binary system to determine the solubility of Sn in the A2 (Cr) solid solution, but also in the Cr-Nb-Sn ternary system in order to determine phase equilibria of the isothermal section at 800°C and 1100°C. Besides, the formation enthalpies of all the ordered configurations of the C15 and A15 phases and the stoichiometric Nb6Sn5 and NbSn2 phases have been calculated using the Density Functional Theory (DFT). The mixing enthalpies of the A2 binary solid solutions have been estimated using the Special Quasirandom Structures (SQS). All these new experimental and calculated data have been taken into account for a new thermodynamic assessment of the three binary and the ternary systems.

      PubDate: 2017-03-12T21:13:18Z
       
  • Thermochemical analysis for the reduction behavior of FeO in EAF slag via
           Aluminothermic Smelting Reduction (ASR) process: Part Ι. Effect of
           aluminum on Fe & Mn recovery
    • Abstract: Publication date: Available online 6 March 2017
      Source:Calphad
      Author(s): Jung Ho Heo, Joo Hyun Park
      We investigated Fe recovery from EAF slag by means of Aluminothermic Smelting Reduction (ASR) at 1773K, especially the quantitative effect of initial Al/FeO molar ratio upon the Fe recovery. Both calculated and experimentally measured system temperatures continuously increased with increasing initial Al/FeO molar ratio. Furthermore, to predict the reduction behavior we calculated variations in the slag composition by using FactSage™ 7.0 software. FeO and Al2O3 contents in molten slag varied sharply within the first 5min of the reaction and stabilized soon thereafter. The aluminothermic reduction of FeO appeared to proceed rapidly and in good stoichiometric balance, based upon the mass balance between the consumption of FeO and MnO (ΔFeO and ΔMnO) and the production of Al2O3 (∆Al2O3). Adding an optimal amount of Al (Al/FeO molar ratio ~ 0.8) yielded a Fe recovery of about 90%. Furthermore, the Mn could also be reduced from the EAF slag in the case of excess Al addition (Al/FeO≥0.8). The solid compound spinel (MgO·Al2O3) was precipitated from the slag during the FeO reduction, as confirmed by means of XRD analysis and thermochemical computations. Herein, the mechanism of ASR reaction between FeO in molten slag and Al is explained in several steps.

      PubDate: 2017-03-08T20:58:42Z
       
  • Thermochemical analysis for the reduction behavior of FeO in EAF slag via
           Aluminothermic Smelting Reduction (ASR) process: Part II. Effect of
           aluminum dross and lime fluxing on Fe and Mn recovery
    • Abstract: Publication date: Available online 6 March 2017
      Source:Calphad
      Author(s): Jung Ho Heo, Joo Hyun Park
      We investigated Fe recovery from EAF slag by means of aluminothermic smelting reduction (ASR) at 1773K with Al dross as the reductant, especially the effect of the added amount of the fluxing agent CaO on the Fe recovery. The maximum reaction temperature calculated using FactSage™ 7.0 decreased with increasing CaO addition, but the experimentally measured maximum temperatures increased with increasing CaO addition. We calculated the amounts of various phases before and after Al dross addition under different conditions of added CaO. FeO and Al2O3 contents in molten slag sharply varied within the first 5min of the reaction, stabilizing soon thereafter. The aluminothermic reduction of FeO appeared to proceed rapidly and in good stoichiometric balance, based upon the mass balance between the consumption of FeO and MnO (ΔFeO and ΔMnO) and the production of Al2O3 (∆Al2O3). Iron recovery from EAF slag was maximized at about 90% when 40g of CaO was added to 100g slag. Furthermore, Mn could also be reduced from the EAF slags by the metallic Al in the Al dross reductant. The solid compounds of spinel (MgO∙Al2O3) and MgO were precipitated from the slag during the FeO reduction reaction, as confirmed by means of XRD analysis and thermochemical computations. To maximize Fe recovery from EAF slag, it is crucial to control the slag composition, namely to ensure high fluidity by suppressing the formation of solid compounds.

      PubDate: 2017-03-08T20:58:42Z
       
  • Thermodynamic modeling of the quaternary Al-Cu-Mg-Si system
    • Abstract: Publication date: June 2017
      Source:Calphad, Volume 57
      Author(s): Senlin Cui, In-Ho Jung
      Based on the critically evaluated thermodynamic and phase diagram information available in the literature, thermodynamic modeling of the Cu-Mg, Al-Cu-Mg, Al-Cu-Si, and Cu-Mg-Si systems were conducted using the CALPHAD (CALculation of PHAse Diagrams) technique. The liquid phase was described using the Modified Quasi-chemical Model (MQM), and the solid solution phases were modeled with the Compound Energy Formalism (CEF). Based on the newly obtained and the previously published thermodynamic descriptions of the subsystems, a set of self-consistent thermodynamic description for the Al-Cu-Mg-Si quaternary system was constructed. Comprehensive comparison between the calculated and measured thermodynamic and phase diagram information indicated that most of the reliable experimental data in the quaternary system can be satisfactorily reproduced by the presently obtained thermodynamic description. The optimized thermodynamic parameters can be used for the calculations of the phase diagram and thermodynamic properties of any composition and temperature range in the Al rich Al-Cu-Mg-Si quaternary system.

      PubDate: 2017-03-03T04:04:58Z
       
  • Experimental investigation and thermodynamic assessment of the Li-Sb
           system
    • Abstract: Publication date: June 2017
      Source:Calphad, Volume 57
      Author(s): Fan Zhang, Shuhong Liu, Jianchuan Wang, Yong Du, Lixian Sun
      Sb and Sb-containing compounds have been attracting a great interest as promising alternative materials for commercial anodes and liquid batteries. The Li-Sb system was studies experimentally by investigating 6 alloys with X-ray diffraction measurement, scanning electron microscopy and electron probe microanalyses. Two binary phases Li2Sb and Li3Sb were confirmed to be stable in this system. Two invariant reactions L→(Sb)+Li2Sb and L+Li3Sb→Li2Sb were identified experimentally based on the microstructures of the as-cast alloys. The eutectic point was determined to be about 40at% Li. The enthalpies of formation for Li2Sb, αLi3Sb and βLi3Sb at 0K were calculated by means of density functional theory and the transition enthalpy between αLi3Sb and βLi3Sb was obtained. Then, the presently obtained results, combined with a critical review of literature data, were used to develop the thermodynamic description of the Li-Sb system by means of CALPHAD method. The liquid phase was treated as (Li, Li3Sb, Sb) using an associate model. The calculated phase diagram and thermodynamic properties can reproduce the available experimental data reasonably.

      PubDate: 2017-03-03T04:04:58Z
       
 
 
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