Application of titanium alloy

Titanium alloy has high strength, low density, good mechanical properties, good toughness and corrosion resistance. In addition, titanium alloy has poor process performance and difficult cutting. In hot working, it is very easy to absorb hydrogen, oxygen, nitrogen, carbon and other impurities. In addition, the anti-wear property is poor and the production process is complex. The industrial production of titanium began in 1948. With the development of aviation industry, titanium industry grows at an average annual rate of about 8%. At present, the annual output of titanium alloy processing materials in the world has reached more than 40000 tons, and there are nearly 30 kinds of titanium alloy brands. The most widely used titanium alloys are Ti-6Al-4V (TC4), ti-5al-2.5sn (TA7) and commercially pure titanium (TA1, TA2 and TA3).

Titanium alloy is mainly used to make aircraft engine compressor parts, followed by rocket, missile and high-speed aircraft structural parts. In the mid-1960s, titanium and its alloys have been used in general industry, such as electrodes for electrolysis industry, condensers for power stations, heaters for oil refining and seawater desalination, and environmental pollution control devices. Titanium and its alloys have become a kind of corrosion-resistant structural materials. In addition, it is also used to produce hydrogen storage materials and shape memory alloys.

In 1956, China began the research on titanium and titanium alloy, and in the mid-1960s, it began the industrial production of titanium materials and developed TB2 alloy.

Titanium alloy is a new important structural material used in aerospace industry. Its specific gravity, strength and service temperature are between aluminum and steel, but its specific strength is high, and it has excellent seawater corrosion resistance and ultra-low temperature performance. In 1950, the United States first used the F-84 fighter bomber as the rear fuselage heat shield, wind shield, tail cover and other non bearing components. Since the 1960s, the use of titanium alloy has shifted from the rear fuselage to the middle fuselage, and partly replaced structural steel to make important load-bearing components such as partition frame, beam, flap slide rail, etc. The amount of titanium alloy used in military aircraft increases rapidly, reaching 20% - 25% of the weight of aircraft structure. Since the 1970s, a large number of titanium alloys have been used in civil aircraft, such as Boeing 747, which uses more than 3640 kg of titanium. Titanium is mainly used to replace steel for aircraft with Mach number less than 2.5 to reduce structural weight. Another example is the US SR-71 high-altitude high-speed reconnaissance aircraft (flying Mach number is 3 and flying altitude is 26212m), which is known as "all titanium" aircraft. Titanium accounts for 93% of the structural weight of the aircraft. When the thrust to weight ratio of aero-engine increases from 4 to 6 to 8 to 10, and the outlet temperature of compressor increases from 200 to 300 ° C to 500 to 600 ° C correspondingly, the original low-pressure compressor disk and blade made of aluminum must be made of titanium alloy, or the high-pressure compressor disk and blade made of titanium alloy instead of stainless steel, so as to reduce the structural weight. In the 1970s, titanium alloy generally accounted for 20% ～ 30% of the total structural weight of aero-engine. It was mainly used to manufacture compressor components, such as forged titanium fan, compressor disk and blade, cast titanium compressor casing, intermediate casing, bearing shell, etc. The spacecraft mainly uses the high specific strength, corrosion resistance and low temperature resistance of titanium alloy to manufacture various pressure vessels, fuel tanks, fasteners, instrument straps, frames and rocket shells. Titanium alloy plate welding parts are also used in artificial earth satellites, lunar module, manned spacecraft and space shuttle.