1、Titanium Aluminides Intermetallics R.J Song TongjiUniversity Contents Introduction Basic information about TiAl Manufacturing techniques Ways to improve the RT ductility Conclusion Rocket Shroud Background high-temperature structural materials Development of new structural materials used at high tem
2、perature is important and essential to take the first step in aerospace industry. Aircraft Traditional materials1 Ti alloys Ni alloys Highest used temperature 600 1100 Density 4.5g.cm-3 8.3g.cm-3 LPT Blades(by casting) Tuebo Charger(by casting) (Tetusi 2005) Advantage of titanium aluminides2 Low den
3、sity Good corrosion,creep and oxidation resistance High strength High stiffness -2Ti3Al ,2TiAl 基合金与常规 Ti 基合金、 Ni 基高温合金的性能比较 3 Advantage of titanium aluminides Intermetallic and Alloys Crystal structure forTiAl(a) and 2Ti3Al(b) Phases of titanium aluminides Of the intermetallic compound phases identi
4、fed in Ti-Al alloys, Ti3Al(2), TiAl(), Al2Ti and Al3Ti phases are stable at room temperature.5 2 2+ Alloy composition and microstructure 5 Of these phases, only the Ti3Al (2), and TiAl () phases have been found to be of any engineering significance. FL NL DP NG Phases of titanium aluminides at 50% A
5、l pure gamma phase exhibiting no ductility. Crystal structure forTiAl L10 Phases of titanium aluminides at, not depend on the direction of ) show anisotropic microstructures as well as significant texture and segregation. 44.6% 49.4% Ti-Al44-Nb4-Mo0.5-Cr1.5-B0.1-Y0.1(wt%) Effect of Al13 42-45%Al,sol
6、idify via the body-centered cubic -phase: L L+ +(the preferential directions of crystal growth are 1 0 0, 0 1 0 and 0 0 1 and the orientation relationship of and are: 110/(0001) and /) exhibit an isotropic, equiaxed and texture-free microstructure with modest micro-segregation. 44.6% 49.4% Ti-Al44-Nb4-Mo0.5-Cr1.5-B0.1-Y0.1(wt%) solifiying11 L L+ + + 2+ Te(1387K)15(0001)2/111 2/ 110 在高 Al合金中 相先析出 板条 ,随后 再有序化为 2. 在低 Al合金中 相先有序化为 2,随后再析出 板条 . Eutectoid reaction: 2+
