Classification Of Pure Titanium And Titanium Alloys By Major Applications

Titanium is an important structural metal developed in the 1950s. Titanium alloys are widely used in various fields because of their high strength, good corrosion resistance and heat resistance. Many countries in the world have recognized the importance of titanium alloy materials, and successive research and development of titanium alloy materials, and applied in practice. 1950s to 1960s, titanium alloys are mainly used in the development of high-temperature titanium alloy fuselage of aircraft engine structure, the 1970s inspired a number of titanium alloys, and since the 1980s, titanium alloys and high-strength titanium alloys have been further developed. Titanium alloys are mainly used in the manufacture of aircraft engine compressor parts, followed by rockets, missiles and high-speed aircraft structural parts.

Titanium is an allotropic isomer, melting point 1668 ℃, in less than 882 ℃ was a dense row of hexagonal lattice structure, known as α titanium; 882 ℃ with body-centered cubic lattice structure, known as β titanium. For the different characteristics of the above two structures of titanium, add appropriate alloying elements, gradually change its phase transition temperature and phase content, to obtain different microstructure of titanium alloy (titanium alloy). At room temperature, titanium alloys have three types of matrix organization, and titanium alloys are classified into the following three types: α-alloys, (α+β) alloys and β-alloys. China is represented by TA, TC and TB respectively.

Alpha Titanium Alloy

It is a single-phase alloy composed of alpha-phase solid solutions. It is a phase at general and higher application temperatures. The microstructure is stable, the wear resistance is higher than pure titanium, and the oxidation resistance is strong. It can still maintain strength and creep resistance at 500～600℃, but it cannot be strengthened by heat treatment and the room temperature is not high.

β Titanium Alloy

Is composed of single-phase alloy β-phase solid solution, titanium alloy (3) without heat treatment that has high strength, quenched and aged alloy is further strengthened, the room temperature strength of 1372 ~ 1666MPa; but poor thermal stability, should not be used at high temperatures.

α+β Titanium Alloy

It is a duplex alloy with good comprehensive performance, stable organization, good toughness, plasticity and deformation properties, good hot pressure processability, which can make the alloy quenching and aging strengthening. After heat treatment, the strength is increased by 50% to 100 than the annealed state; high temperature strength, can work for a long time at a temperature of 400 ℃ to 500 ℃, titanium alloys have good thermal stability.

The three most commonly used titanium alloys are α-titanium alloy and α+β-titanium alloy. α-titanium alloy has the best cutting and machinability, α+β-titanium alloy is the next best, and β-titanium alloy is the worst. α-titanium alloy is TA, β-titanium alloy is TB, and α+β-titanium alloy is TC.

Titanium alloys can be divided into heat-resistant alloys, high-strength alloys, corrosion-resistant alloys (titanium-molybdenum, titanium-palladium alloys, etc.), low-temperature alloys, and special-function alloys (titanium-iron hydrogen storage materials and titanium-nickel memory alloys). The composition and properties of typical alloys are shown in the table.

The phase composition and microstructure of heat-treated titanium alloys can be obtained by adjusting the heat treatment process. The generally fine isometric organization has plasticity, thermal stability and good fatigue strength; creep fracture strength, high creep strength and fracture toughness of needle-like structure; mixed isometric and needle-like structure has good overall performance.

Titanium alloy has the advantages of high strength, low density, good mechanical properties, good toughness, good corrosion resistance. In addition, titanium alloy process performance is poor, processing difficulties. It is easy to absorb hydrogen, nitrogen, carbon and other impurities during hot processing. And wear resistance is poor, the production process is complex. Industrial production of titanium began in 1948, and the development of the aviation industry requires the titanium industry to grow at an average annual rate of about 8%. The annual output of titanium alloy processing materials has reached more than 4 tons, has produced nearly 30 grades of titanium alloy materials. The most widely used titanium alloys are Ti-6Al-4V (TC4), Ti-5), Al-2.5Sn (TA7) and industrial pure titanium (TA1, TA2 and TA3).

Titanium alloys are mainly used in the manufacture of aircraft engine compressor parts, followed by structural parts for rockets, missiles and high-speed aircraft. in the mid-1960s, titanium and its alloys have been used in general industry to produce electrodes for the electrolysis industry, condensers for power stations, heaters for petroleum refineries and seawater desalination as well as for environmental pollution control devices, among other applications. Titanium and its alloys have become a corrosion-resistant structural material. In addition, it is also used to produce hydrogen storage materials and shape memory alloys.

China began research on titanium and titanium alloys in 1956, and in the mid-1960s titanium alloys were industrialized and TB2 alloys were manufactured.

Titanium alloy is a new type of important structural material used in the aerospace industry, its strength and temperature ratio between aluminum and steel, aluminum, steel high strength but also has excellent corrosion resistance and low temperature performance. 1950, the United States for the first time in the F-84 fighter-bomber as a rear fuselage heat shields, windshields, tail cover and other non-load-bearing parts. 1960s, Kay began to use titanium alloy parts from the rear of the fuselage to the Fuselage middle transfer, and partially replace structural steel to manufacture bulkheads, beams, flaps, slides and other important load-bearing parts. The amount of titanium alloy used in military aircraft has increased rapidly, reaching 20% to 25% of the weight of the aircraft structure. since the 1970s, civil aircraft began to use titanium alloy in large quantities, such as the Boeing 747 aircraft titanium content of more than 3640 kilograms. Mach number greater than 2.5 aircraft mainly use titanium to replace steel to reduce structural weight. For example, the United States SR-71 high-altitude high-speed reconnaissance aircraft (flight Mach No. 3, flight altitude of 26,212 meters), titanium accounted for 93% of the weight of the structure of the aircraft, known as the "all titanium" aircraft. When the aero-engine thrust-to-weight ratio increased from 4 to 6 to 8 to 10, the compressor outlet temperature correspondingly increased from 200 to 300 ℃ to 500 to 600 ℃, the original made of aluminum low-pressure compressor disk and blade must be titanium alloy, titanium alloy alloy or stainless steel instead of high-pressure compressor disk and blade. To reduce the weight of the structure. 70's, the amount of titanium alloy in the aviation engine generally accounted for 20% ~ 30% of the total weight of the structure, mainly used in the manufacture of pressurized parts, such as forging titanium fan and pressurized air disk and blade, titanium casting spacecraft mainly used to manufacture a variety of high strength, corrosion resistance, low temperature resistance of titanium alloy to manufacture a variety of pressure vessels, fuel tanks, fasteners, bandages, instrument frames and rocket shells. The main use of titanium alloy is to manufacture various pressure vessels, fuel tanks, fasteners, bandages, instrument frames and rocket housings. Artificial Earth satellites, moon landing module, manned spacecraft and the space shuttle also use titanium alloy plate welding parts.