| Abstract: | Ternary Laves phases with transition metals and aluminium were overviewed with respect to their use for structural high temperature applications. The relation between constitution, phase stability, crystal structure and basic mechanical properties was discussed. The crystal structure-hexagonal C14 structure or cubic C15 structure-is a function of atomic radii and valence electron concentration. A strong positive correlation of basic mechanical properties-hardness, yield stress-with the sublimation energy of the phases was found. The brittle to ductile transition temperature was observed at about 60% of the melting temperature. The regarded ternary Laves phases allow alloying to form stable equilibria with the less hard and brittle B2 aluminides. Advantageous examples are alloys of type NbNiAl NiAl, TaNiAl NiAl, and TaFeAl FeAl. Multiphase NiAl Ta Cr alloys are regarded as promising for structural high temperature applications and have been selected for a materials development which aims at applications in gas turbines at temperatures above those of Ni base superalloys, such alloy can be prepared by ingot metallurgy and powder metallurgy and hot forming is possible. Characteristic data were presented with respect to mechanical behaviour. The alloys showed a high thermoshock resistance in spite of the comparatively high brittle to ductile transition temperature. The prospects of alloy development were discussed. |
