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Phase Stability of MoSi2 with Cr Additions

Published online by Cambridge University Press:  01 January 1992

P. S. Frankwicz ,
J. H. Perepezko  and
D. L. Anton
P. S. Frankwicz
Affiliation:
Dept. of Materials Science and Engineering, University of Wisconsin-Madison, 1509 University Ave., Madison WI. 53706, USA
J. H. Perepezko
Affiliation:
Dept. of Materials Science and Engineering, University of Wisconsin-Madison, 1509 University Ave., Madison WI. 53706, USA
D. L. Anton
Affiliation:
United Technologies Research Center, East Hartford CT. 06108, USA.
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Abstract

The phase stability of MoSi2 with Cr additions has been investigated in order to explore the issues of ternary solubility and structural stability of MoSi2- The solidification microstructure of MoSi2-rich alloys, along the MoSi2-CrSi2 ternary section, displays a two phase mixture of primary MoSi2 (C11b) and intercellular ternary CrSi2 (C40). The development of the phase equilbria between the C11b and C40 disilicides, as observed in this system, is characteristic of a broad class of intersilicide reactions involving MoSi2. The issues of chemical reactivity and structural stability of MoSi2 composite designs underscores the importance of phase equilibria investigations. The solubility of Cr in annealed MoSi2 was observed to be on the order of 3 atomic percent. Past studies demonstrated that Ti and Ta have limited solution in MoSi2; the minor solubility of Cr in MoSi2 corroborates the trend of limited solubility of transition metals in the MoSi2 (C11b) structure. The relatively small changes in the lattice parameters of MoSi2 with Cr additions point to an inability of the C11b disilicide structure to accommodate the lattice perturbation resulting from solute atoms. The observations of this investigation suggest that the phase stability of MoSi2 is primarily controlled by geometrical factors.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 288: Symposium L – High-Temperature Ordered Intermetallic Alloys V , 1992 , 159
Copyright
Copyright © Materials Research Society 1995

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References

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