1. High strength and toughness β Type I titanium alloy
β Type I titanium alloy has good processability, is easy to forge, roll and weld, and can obtain high strength and fracture toughness through solution aging treatment. At present, it has obtained high strength and toughness for practical application in aircraft β Type I titanium alloys mainly include the following:
Ti-1023 (Ti-10V-2Fe-3Al) titanium alloy was developed by American Timet Company in 1971. It is a forged titanium alloy with high structural efficiency, high reliability and low manufacturing cost to adapt to the damage tolerance design principle. The Al equivalent of this alloy is 4.0, and the Mo equivalent is 11.1（ α+β)/β The phase transition temperature is 790~805 ℃, which has greater hardenability, significant heat treatment strengthening effect and excellent forging performance. Isothermal forging can be carried out at 760 ℃, providing various near net machined forgings. After heat treatment σ B is 965 ～ 1310MPa, KIC is 99 ～ 33 MPa · m1/2. It has been used for the landing gear main beam of Boeing 777 passenger aircraft and the main landing gear strut of Airbus A380.
Ti-l5-3 (Ti-15V-3Cr 3Al - 3Sn) high strength β Titanium alloy was developed in the 1970s under the support of the US Air Force β High strength corrosion-resistant alloy. The Al equivalent and Mo equivalent of the alloy are 5.0 and 15.7 respectively（ α+β)/β The phase transition temperature is 750~770 ℃. It has excellent cold deformation, age hardening and weldability. Its cold workability is better than that of industrial pure titanium. It can be used for cold forming of various complex parts in the solid solution state. It has small crack sensitivity σ B ≥ 1310MPa, this alloy is particularly suitable for manufacturing rocket engine propellant tanks, conduits and other components, and has been applied to the application control system pipes and fire extinguishers on the Boeing 777.
β- 21S (Ti-15Mo-3Al-2.7Nb-0.2Si) alloy is an anti-oxidation and ultra-high strength titanium alloy developed by American Timet Company in 1989. The Al equivalent of the alloy is 4.0, and the Mo equivalent is 15.8（ α+β)/β The phase transition temperature is 793 ～ 810 ℃, which has good oxidation resistance and can work at 540 ℃ for a long time; Excellent cold and hot working performance. After heat treatment, σ b=1150～1350MPa， δ 5=6%～8%。 The alloy is suitable for engine liner and nozzle, and has been used as the matrix material of silicon carbide/titanium composite by NASA.
BT22 (Ti-5Al-5Mo-5V-1Fe-1Cr) alloy is a high strength alloy developed in Russia in the 1970s β Type I titanium alloy. The Al equivalent of the alloy is 6.0, and the Mo equivalent is 11.8（ α+β)/β The phase transition temperature is 860 ～ 990 ℃, which has good processing and welding properties. It is mainly used to produce die forgings. Its quenching depth reaches 200mm σ b≥1105MPa。 The alloy can be used to manufacture fasteners for fuselage, wing force bearing parts and operating system, etc. that work at 350~400 ℃ for a long time, and also can be used to manufacture fan disks and blades of engines that work at temperatures below 350 ℃. It has been used for the fuselage, wing, landing gear and other high load bearing parts of 1L-86 and 1L-96-300.