Titanium is an important structural metal developed in the 1950s. It has high strength, corrosion resistance and heat resistance. In the 1950s and 1960s, the development of high temperature titanium alloy for aero-engine and structural titanium alloy for airframe was mainly carried out. A number of corrosion resistant titanium alloys were developed in the 1970s. Since the 1980s, corrosion resistant titanium alloys and high strength titanium alloys have been further developed. Titanium alloy is mainly used to make aircraft engine compressor parts, followed by rocket, missile and high-speed aircraft structural parts.
The first practical titanium alloy was ti-6al-4v alloy developed successfully in the United States in 1954. Due to its good heat resistance, strength, plasticity, toughness, formability, weldability, corrosion resistance and biocompatibility, it has become the leading alloy in the titanium alloy industry. Many other titanium alloys can be considered as modification of ti-6al-4v alloy.
Titanium alloy is an alloy based on titanium with other elements added. Titanium has two homogenous different crystal: under 882 ℃ to close the six-party alpha titanium structure, above 882 ℃ for body centered cubic beta titanium.
Oxygen, nitrogen, carbon and hydrogen are the main impurities of titanium alloys. Oxygen and nitrogen have a large solubility in the q phase, which has a significant strengthening effect on titanium alloy, but the plasticity decreases. Generally, the content of oxygen and nitrogen in titanium is below 0.15 ~ 0.2% and 0.04 ~ 0.05%, respectively. Hydrogen has a small solubility in the q phase, and too much hydrogen in the q alloy will result in hydride, which will make the alloy brittle. Hydrogen content in titanium alloys is usually controlled below 0.015%. Hydrogen dissolved in titanium is reversible and can be removed by vacuum annealing.
Titanium is a new type of metal. Its properties are related to the content of carbon, nitrogen, hydrogen, oxygen and other impurities. 99.5% of industrial pure titanium performance is: the rho = 4.5 g/cm3 density, melting point is 1725 ℃, coefficient of thermal conductivity of lambda = 15.24 W/(m.K), tensile strength of sigma b = 539 mpa, elongation delta = 25%, reduction of area bits = 25%, elastic modulus E = 1.078 x 105 mpa, hardness HB195.
