Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
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Problems in Thermodynamic Analyses in a Fe-Cr-Ni-Mo System Alloy
Hidekazu Todoroki
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2019 Volume 105 Issue 3 Pages 358-362


Thermodynamic data including interaction coefficients necessary for molten Fe-Cr-Ni-Mo system alloys have not been sufficient to calculate terminal compositions in equilibrium as a result of some reaction. Particularly, the coefficients in relation with Mo are insufficient so that the corresponding coefficients have to be neglected usually. In this status, eAlMo = 0.007 was estimated by regularity according to atomic number after rearranging the other coefficients related to the activity coefficients for Al according to periodical table. Applying the value for the stability diagram of MgO / MgO·Al2O3 / Al2O3 previously reported by the author, the boundaries did not vary so much.

Subsequently, interaction coefficients related to the activity coefficients for Si, used as deoxidant the same as Al, were also rearranged with periodical table resulting in finding less clear periodic relation than Al. In particular, the values of eSiTi so far reported have significant deviation between the researchers leading to the difficulty in prediction about the terminal compositions in equilibrium when considering some reactions. Furthermore, the value of eSiMo = 0.11 recently proposed could describe the lower attained oxygen content in SUS316L containing 2 mass% Mo than that of SUS304 stainless steels. Finally, it is truly expected that the interaction coefficients related to Mo is made clear in the near future.

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© 2019 The Iron and Steel Institute of Japan
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