titanium alloys Classification
α and near α titanium alloy
Compared with other titanium alloys, such as α + β alloy, its strength is lower and can not be strengthened by heat treatment. Its main characteristics are good high temperature performance, stable structure, good welding, corrosion resistance and thermal stability. Its disadvantage is poor plasticity in hot working. Nearly α titanium alloy is the basis for the development of heat-resistant titanium alloy, and is the direction of the development of high-temperature titanium alloy in the world. BT20 (TA15) is the most widely used titanium alloy in aircraft, which is mainly used to make the wall plate, frame, beam and other structural parts of aircraft body. Near α titanium alloy can also be used in the fabrication of aircraft skin, engine blade and disk, ultra-low temperature container, space vehicle fuel storage.
α + β
α + β titanium alloy
It has good comprehensive mechanical properties and processing properties. It is a medium strength titanium alloy, which can be heat treated and strengthened. It has good heat resistance at medium temperature, but its structure is not stable. It can be processed into bar, profile, plate, forging, die forging and so on. In the aviation industry, it is mostly used to manufacture aircraft blades, plates and some fasteners. TC4 (Ti-6Al-4V) is the most widely used titanium alloy in the aircraft. It is mainly used to make the wall plate, frame, beam and other structural parts of the aircraft body. It represents the world's highest level fighter plane, F22, with 36 tons of titanium for structure and 5 tons for 2 engines. Its fuselage partition frame adopts Ti-6Al-4V overall structure, which needs to provide unprecedented large-scale titanium alloy die forgings, thus significantly increasing the difficulties in large-scale billet preparation, filling molding and tissue control.
Metastable alloy
After solution aging, high room temperature strength and good fatigue property can be obtained, but the high temperature structure is not stable, and the heat resistance and welding performance are relatively poor. At present, it is mainly used for long-term work below 250 ℃ or short-term work below 350 ℃, such as aircraft structural parts and fasteners. TB6 (time 10-2-3) and TC18 (BT22) are the most widely used high-strength titanium alloys in aircraft, which are used to make landing gear, frame, beam, rib and joint of aircraft. This kind of alloy is the most potential alloy type of high strength and high toughness titanium alloy with high structural benefit.
Stable β - alloy
Due to the relatively large density and poor plasticity, this kind of alloy has no industrial application.
