COST 507 - Repositório Aberto da Universidade do Porto
COST 507 - Repositório Aberto da Universidade do Porto
COST 507 - Repositório Aberto da Universidade do Porto
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Extrapolations based on Ti-C-N<br />
S3<br />
Bo Sundman and Lucia F.S. Dumitrescu<br />
Division of Computational Termodynamics<br />
Department of Materials Science and Engineering<br />
Royal Institute of Technology<br />
Sweden<br />
Abstract<br />
The binary systems Ti-C and Ti-N are important in many metallic ternary systems.<br />
There have been difficulties during the <strong>COST</strong> project to reconcile many experimental<br />
observations in ternary systems involving Ti-C and Ti-N. Due to low solubilities it<br />
has not been possible to resolve the difficulties by using ternary parameters. This<br />
means that one has to reassess binary systems using ternary information.<br />
There is a great risk that different groups in <strong>COST</strong> make different adjustments to the<br />
same binary system to fit their ternary. It is difficult to judge the importance of the<br />
different <strong>da</strong>ta and each group has the wish to present as good description of its<br />
systems as possible.<br />
This presentation attempts to show how the Ti-C and Ti-N systems behave in some<br />
ternary systems and suggests a modification of the current Ti-C and a new Fe-Ti<br />
assessment. Different ΑΙ-Ti assessments are compared also. The ternary systems<br />
considered are Al-Ti-C, Al-Ti-N, Fe-Ti-N, Fe-Ti-C, Ni-Ti-C and Ti-C-N. Among<br />
other important systems still not checked are Co-Ti-C and W-Ti-C.<br />
1. Introduction<br />
Titanium carbonitride has a strong technical importance, e.g. in hard materials<br />
[92Cla] and in microalloyed steels [92Zou]. It should thus be interesting to assess its<br />
thermodynamic properties. The problem is that one should like to account for its<br />
equilibria in several systems. When such information shows inconsistencies it may be<br />
justified to include even more systems in order to choose between different<br />
alternatives. Thus, the main part of the present discussion will concern TiC and TiN<br />
in equilibrium with other phases in the Ti-C-N-Al-Ni-Fe system.<br />
Jonsson has published an impressive group of assessments resulting in a selfconsistent<br />
set of descriptions of the systems W-Ti-C-N [96dJon] and Fe-Ti-C-N<br />
[97Jon] and their subsystems. Some objections have been raised to his description of<br />
the Ti-N [96aJon] and Ti-C [96bJon] systems and have resulted in a different<br />
termodynamical description of the Ti-N system, Zeng et al. [96Zen], and of the Ti-C<br />
system , Dumitrescu [97Dum]. But there are also independent assessments of the Ti-<br />
N system by Ohtani et al. [90Oht] and of the Ti-C system by Albertsen et al. [95Alb]<br />
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