COST 507 - Repositório Aberto da Universidade do Porto
COST 507 - Repositório Aberto da Universidade do Porto
COST 507 - Repositório Aberto da Universidade do Porto
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Jonsson combined his descriptions of the TiC and TiN systems to describe the TiC<br />
N [96cJon] system but had to introduce strong ternary interactions, in particular in the<br />
TiCTiN section. Before a similar attempt was made, using the new assessment of the<br />
TiC system by Dumitrescu, an analysis was made of the information on the<br />
equilibrium between titanium carbonitrides of various compositions and liquid Fe<br />
[90Ozt]. It indicated that the interaction energy in the TiCTiN section may be<br />
around 18000 J/mol which is about one third of Jonsson's [96cJon] value. This new<br />
value was then used by Dumitrescu in an assessment of the TiCN system, in<br />
combination with the new description of TiC. Jonsson's [96aJon] description of the<br />
TiN system was used. The result was rather satisfactory as demonstrated in Figs. 11,<br />
12, 13 and 14.<br />
5.2 The Al-Ti-C system<br />
It was pointed out by Seifert et al. [96Sei] that the experimental fourphase<br />
temperature for L + TiC + ALC 3 + Al 3 Ti in the TiAlC system strongly favours the<br />
higher values of A f °H. It should be noticed that the use of this information<br />
depends on choices for A1 4 C 3 and Al 3 Ti. Several<br />
examined.<br />
alternatives should thus be<br />
The equilibrium temperature has been reported to be 1085 K which is not far from<br />
the melting point of Al. Thus, G m of pure liquid Al at this temperature is well<br />
established. The effect of Ti and C on G m of L is not very large because of the low<br />
contents of Ti and C. One can thus use any descriptions of the liquid phase in the Al<br />
Ti and AlC systems in a calculation of the fourphase equilibrium. G m of Al 3 Ti is<br />
obtained from assessing the ΑΙTi system. There are two such assessments, by<br />
Saunders [94Sau] and by Zhang [96Zha]. We should thus use two values in our test.<br />
For ALtC 3 an older value was used by Gròbner et al. [95Grö] but recently Meschel<br />
[95Mes] gave a different value and Lukas [96Luk] modified the AlC system<br />
description. For TiC Jonsson's [96bJon] description gave very low values and the<br />
experimental temperature thus gives strong preference for less negative value.<br />
Dumitrescu's value gave the following values<br />
[94Sau] + [96Luk]<br />
[94Sau] + [95Grö]<br />
[96Zha] +[96Luk]<br />
[96Zha] + [95Grö]<br />
908 K<br />
1061 K<br />
854 K<br />
1033 K<br />
These results give strong preference for the old value of A1 4 C 3 and some preference<br />
for Saunders' [94Sau] description of AlTi.<br />
5.3 The Ti-Ni-C system<br />
Schuster et al. [97Sch] have studied the solubility of TiC in fee Ni at equilibrium with<br />
graphite and compared with calculations and previous experiments. Experiments fell<br />
between calculated results based on Jonsson's , Fig.15, and Dumitrescu's values for<br />
TiC, Fig. 16. However, Schuster et al. used an assessment of NiTi by Bellen [96Bel].<br />
181