Tailored Interfaces for Metal-Matrix Composites-Fundamental Considerations

The objective of this research is to determine the interface properties needed for successful metal matrix composites and to learn how to achieve these properties. A number of factors have been selected for the study. These are thermodynamic stability of the interface, nature of the bonding across the interface, energy and structure of the interface, and role of adsorption at the interface. A number of systems have been chosen to probe these factors; namely, Al/TiC, Al/alpha-Al2O3, A1/MgAl2O4(spinel), Al/Al3(Tix, Zr1-x), Mg/SiC, Mg/MgO, and Mg/Al2O3. Techniques for preparing all of these composites have been worked out, including mechanical alloying followed by extrusion, arc melting, and liquid metal infiltration. MMCs also were obtained from Martin Marietta and Dow. Microstructures of the resulting MMCs are presented and discussed along with preliminary studies of some of the interfaces using transmission electron microscopy. In comparison to Al/SiC, Al/TiC and Mg/SiC show no evidence of chemical reaction at the interface during processing. Al/MgAl2O4(spinel) has superior mechanical properties to Al/alpha-AlO3, both prepared identically. (Author) (tr)