A high niobium titanium aluminum alloy is composed of titanium, aluminum, niobium, carbon, tungsten and yttrium. Its characteristics are as follows :Al content is 45 -- 46%,Nb content is 8 -- 10%,C content is 0 -- 0.2%,W content is 0 -- 0.2%, Y content is 0 -- 0.1%, all of which are atomic percentage and allowance is Ti. The microstructure of the alloy is composed of two ordered phases γ and α2, and the uniform fine lamellar microstructure is obtained in the deformed alloy and the cast alloy, the grains are 100-150μm, the lamellar spacing is 0.3-0.4μm. Its advantages are that the temperature of high NbTiAl alloy can reach 840-900℃.
TiAl alloy has been recognized as the most promising intermetallic structural material. At present, the developed TiAl composition is roughly in the range of Ti-45/48Al-0/2M-0/5x-0/2Z (M = Cr, Mn, V, X = Nb, Ta, W, Z = Si, B, C, N). M alloy elements are favorable for plasticity and recrystallization. niobium and tantalum are the main solution strengthening elements. A small amount of W and Sn also have similar effects, while Si, B, N and C precipitate the second phase Ti5Si3 and TixAlC to strengthen the grain, and B to refine the grain, but may increase the wafer spacing. At present, casting alloy has entered the stage of practical application.
At present, the deformed TiAl alloys under research and development include Ti-46Al-4Nb-1W, Alloy K5(Ti-46.5Al-2Cr-3NB-0.2W), etc. After forging and heat treatment, these alloys have a yield strength of 400-600mpa at room temperature, a elongation of 1-3, and good high temperature strength at 500-750℃. The typical microstructure of K5 alloy RFL is σY473MPa, σB557MPa, δ % 1.2. The total lamellar structure (TMPL) obtained by a special thermo-mechanical treatment increases the yield strength σY775MPa at room temperature.
Most of the TiAl alloys developed in China are basically similar to the common TiAl alloys abroad, while some are slightly different in composition and have no fundamental difference in mechanical properties. All of them belong to the common TiAl alloys. The high nb TiAl alloy we studied belongs to high temperature and high performance TiAl alloy. The composition, strength and oxidation resistance of TiAl alloy are completely different from those of common TiAl alloy, and the service temperature is increased by 60-100℃. Our study promotes the development of high temperature and high performance TiAl alloy.
The purpose of the present invention is to improve the service temperature of the common TiAl alloy, that is, to improve the strength and oxidation resistance of the common TiAl alloy, so that the high nb TiAl alloy can be used at 840-900℃.
