ICAMS / Interdisciplinary Centre for Advanced Materials Simulation
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Improvements in the thermodynamic descriptions of the Fe-based systems

Date: 27.05.2012
Place: The 3rd International Symposium on Steel Science, Kyoto, Japan

Taichi Abe, National Institute for Materials Science, Tsukuba, Ibaraki, Japan
Kiyoshi Hashimoto
Yukiko Sawada
Cenk Kocer
Kazuhisa Shobu
Mauro Palumbo
Suzana Fries
Masato Shimono
Kaneaki Tsuzaki

A thermodynamic database for the Iron based systems was first released in early 90’s [1]. Since then it has been extensively developed for many years because of the practical importance of the Fe-based alloys. Currently, several databases are available for  hermodynamic calculations of the Fe-based systems using various thermodynamic software packages, such as Fe-data for Thermo-Calc [2], FS-Steel for FactSage [3], and PanFe for PANDAT [4]. These databases cover most of the constituting elements (20-30 elements) and phases (~100 phases) of the Fe-based alloys and seem to have been developed successfully. However, there remain several issues which require further development. For example, the valid range of alloy compositions is usually lower than 50 at.% in the sum total of additives to Fe. Because of this limitation, for high-alloyed steels such as marage steels, calculated phase equilibria with intermetallic compounds (e.g. TCP phases [5]) are not satisfactory in some cases. Another limitation would be Gibbs energy descriptions of phases, which precipitate only under very limited conditions, such as the Z phase (a complex nitride) in high-Cr heat resistant steels [6], and the M6C phase [7] in low-alloyed and tool steels. To improve on these issues, the single most important difficulty to address is that the databases are closed-databases; that is, they are not publicly available.

Therefore, in our open-database [8] we are improving on existing data of the Fe alloys by implementing ab initio simulations of material properties and by refining the thermodynamic models, and procedures, of the thermodynamic assessments.

[1] TC-Fe6, TCS Steels/Fe-alloys database (2009), Thermo-Calc software AB, Sweden.
[2] Fe-data ver.6, TT Fe-alloys database (2005), Thermotech Ltd., U.K.
[3] FSStel, FactSage Steel database (2011), Thermfact, Canada, and GTT-Tech., Germany.
[4] PanIron, PANDAT Fe alloy database (2010), CompuTherm LLC, U.S.A.
[5] M.Palumbo, T.Abe, S.G.Fries, A.Pasturel: Phys. Rev. B, 83, 14, 144109 (2011).
[6] C.Kocer, T.Abe, A.Soon: J. Mater. Sci. Eng. A, 505, 1-5 (2009).
[7] C.Kocer and T.Abe, unpublished work.
[8] NIMS Thermodynamic database, http://www.nims.go.jp/cmsc/pst/database/

Supporting information:

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