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Abstract

The development of thermodynamic databases has been going for a long time using the present set of available lattice stabilities, as presented in SGTE database [1, 2]. It is well known, however, that these lattice stabilities present some drawbacks and can be improved. For example, there are experimental evidences that the melting temperature of pure Cr is significantly lower than the assessed value used by SGTE (2180 K). Furthermore, till present, lattice stabilities are modeled above room temperature by polynomial expressions with limited physical meaning. In the framework of the Sapiens project, new lattice stabilities are being developing starting from zero K, incorporating available physical models as well as first principles data and trends. Iron and Chromium are the first elements for which this approach is applied.

In this work, experimental data on thermophysical properties for these elements have been collected from the literature. By critically evaluating these experimental data, including the most recent ones, and adopting thermodynamic models as proposed for example in Ringberg workshops and later [3], new lattice stabilities for Cr and Fe are evaluated. The “inverse pyramid effect” [4] has been evaluated for these new lattice stabilities in higher order systems.

References
[1] A. Dinsdale, CALPHAD 15 (1991) 319
[2] UNARY vers. 4.4 database updated from SGTE, www.sgte.org
[3] See i.e. the issue of CALPHAD edited by: B. Sundman, F. Aldinger, CALPHAD 19 (1995)
[4] B. Sundman et al., Changsha, China, 2008, www.csw.edu/MCS02/english.htm