Interfaces in MoSi{sub 2}-SiC in situ composites synthesized by melt processing
- Univ. of California, Santa Barbara, CA (United States)
- Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering
Interfaces between the primary {beta}-SiC and the surrounding MoSi{sub 2} matrix in melt-synthesized in situ composites have been investigated, with emphasis on the chemistry and crystallographic relationships developed during solidification. Primary SiC growth occurs with {l_brace}002{r_brace} and {l_brace}111{r_brace} facets, both of which are found to template the subsequent nucleation and epitaxial growth of the MoSi{sub 2} matrix. Eight independent orientation relationships (ORs) were identified, involving a number of combinations of planes. The interfacial relationships were rationalized using coincident site lattice arguments as well as energetic simulations based on the Grey-Bohr algorithm. The latter analysis suggests that the multiplicity of relationships arises from local effects associated with the size and shape of the adsorbate layers preceding the formation of the MoSi{sub 2} nuclei. An amorphous carbon layer, 2- to 5-nm thick, was detected at all interfaces and some of the matrix grain boundaries. This interphase is believed to evolve by solid-state precipitation of C during postsolidification cooling and is, in principle, metastable. The C interphase enables easy debonding and thus may have important implications for the mechanical performance of materials involving SiC/MoSi{sub 2} constituents.
- Sponsoring Organization:
- Office of Naval Research, Washington, DC (United States); National Science Foundation, Washington, DC (United States)
- OSTI ID:
- 544064
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 9 Vol. 28; ISSN MMTAEB; ISSN 1073-5623
- Country of Publication:
- United States
- Language:
- English
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