Evaluation of the Potential of the Ternary Aluminides in Nb-Ti-Al system for Hiyh Temperature Application

Being aimed to developing intermetallic base structural materials to be worked at above 1000℃, a systematic investigation has been performed of the fundamental crystallographic structure, phase constitution map, density-composition dependence, oxidation resistance and general mechanical behaviour for the ternary intermetallic alloys in the Nb-Ti-Al system. Promissing results have been obtained at the initial stage in the current program. The 1100℃ high temperature strength at the strain rate of 10^-2/s and 10^-5/s for the ternary compound NbTiAl₃ （γ₁） base alloys are generally much higher than that of the binary compound TiAl （γ）, especially in the γ₁ + α₂ phase region, it is as high as twice as that of TiAl. The densities are 4.1-4.79g/cm³, depending on relative amount of the intermetallics involved and the density difference between the intermetallics. The oxidation resistance at the temperature of 900-1200℃ of the compound NbTiAl₃ is relatively low but still acceptable. However, by adjusting the relative amount of constituents and adding a small amount of alloying elements it can be singnificantly improved. The room temperature brittleness remains to be solved.