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A thermodynamic analysis of the Mo-V and Mo-V-C systems
Swedish Inst. for Metals Research.
Swedish Inst. for Metals Research.
2002 (English)In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 26, no 3, 459-503 p.Article in journal (Refereed) Published
Abstract [en]

A new thermodynamic evaluation of the binary Mo-V system and the ternary Mo-V-C system using thermodynamic models for the Gibbs energy of individual phases is presented. The CALPHAD method has been used, with predictions of unknown thermodynamic quantities, to optimize a set of thermodynamic parameters taking related experimental information into consideration. The predictions are based on regularities in bonding properties and vibrational entropy of 3d-transition metal carbides. The results are summarized in tables of thermodynamic parameters, calculated binary phase diagrams and isothermal sections of the ternary phase diagram compared with experimental information. Finally the influence of ternary interaction parameters, especially in the fcc phase, on calculations of equilibria in multicomponent systems is discussed.

Place, publisher, year, edition, pages
2002. Vol. 26, no 3, 459-503 p.
Keyword [en]
Binary alloys, Carbides, Entropy, Gibbs free energy, Isotherms, Molybdenum, Optimization, Phase diagrams, Binary systems
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-7606DOI: 10.1016/S0364-5916(02)00057-3ISI: 000179541200011OAI: oai:DiVA.org:kth-7606DiVA: diva2:12688
Note
QC 20100929Available from: 2005-10-18 Created: 2005-10-18 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Phase equilibria and thermodynamic properties of high-alloy tool steels: theoretical and experimental approach
Open this publication in new window or tab >>Phase equilibria and thermodynamic properties of high-alloy tool steels: theoretical and experimental approach
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The recent development of tool steels and high-speed steels has led to a significant increase in alloy additions, such as Co, Cr, Mo, N, V, and W. Knowledge about the phase relations in these multicomponent alloys, that is, the relative stability between different carbides or the solubility of different elements in the carbides and in the matrix phase, is essential for understanding the behaviour of these alloys in heat treatments. This information is also the basis for improving the properties or designing new alloys by controlling the amount of alloying elements. Thermodynamic calculations together with a thermodynamic database is a very powerful and important tool for alloy development of new tool steels and high-speed steels. By thermodynamic calculations one can easily predict how different amounts of alloying elements influence on the stability of different phases. Phase fractions of the individual phases and the solubility of different elements in the phases can be predicted quickly. Thermodynamic calculations can also be used to find optimised processing temperatures, e.g. for different heat treatments. Combining thermodynamic calculations with kinetic modelling one can also predict the microstructure evolution in different processes such as solidification, dissolution heat treatments, carbide coarsening, and the important tempering step producing secondary carbides.

The quality of predictions based on thermodynamic calculations directly depends on the accuracy of the thermodynamic database used. In the present work new experimental phase equilibria information, both in model alloys containing few elements and in commercial alloys, has been determined and was used to evaluate and improve the thermodynamic description. This new experimental investigation was necessary because important information concerning the different carbide systems in tool steels and high-speed steels were lacking.

A new thermodynamic database for tool steels and high-speed steels, TOOL05, has been developed within this thesis. With the new database it is possible to calculate thermodynamic properties and phase equilibria with high accuracy and good reliability. Compared with the previous thermodynamic description the improvements are significant. In addition the composition range of different alloying elements, where reliable results are obtained with the new thermodynamic database, have been widened significantly.

As the available kinetic data did not always predict results in agreement with new experiments the database was modified in the present work. By coupling the new thermodynamic description with the new kinetic description accurate diffusion simulations can be performed for carbide coarsening, carbide dissolution and micro segregation during solidification.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 68 p.
Keyword
thermodynamic modelling, thermodynamic calculations, tool steels, high-speed steels, CALPHAD
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-453 (URN)91-7178-120-X (ISBN)
Public defence
2005-10-21, salongen, KTHB, Osquars backe 31, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100929Available from: 2005-10-18 Created: 2005-10-18 Last updated: 2010-09-29Bibliographically approved

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