Artificial Composites for High Temperature Applications; A Review (Composites Artificiels Destines a des Applications a Haute Temperature; Un Expose)

摘要

The demands of the aerospace industry and the need for more efficient ground based heat engines have become the main incentives for the development of new higher performance materials. Most monolithic materials lose strength or degrade in properties at higher temperatures. Superalloys, heat resistant alloys and alloys in general, strengthened by conventional mechanisms such as precipitation hardening or mechanical working, exhibit drastic losses in strength at temperatures over 0.7 - 0.8 of their absolute melting points. Dispersion strengthened materials are stronger and more stable than conventional alloys at higher fractions of their melting points ( 0.9). The use-temperatures of ceramics and glasses are often limited by their softening well below their melting points. In Table - 1 some of the materials suitable for high temperature use are listed along with their melting and probable use temperatures. It is well known that, by conventional alloying methods, there will not be any significant increase in the use temperature of the superalloys in the future. Refractory metals are not only costly but are in critically short supply, so a wide commercial use is highly unlikely. Ceramics offer potential in demanding environments, however their inherent problem of brittleness has to be tackled.