The ocean, which covers about 71% of the earth’s surface, is rich in resources. We should develop and utilize the ocean, making it the source of our great wealth, this has been one of the directions people have been trying for many years. But seawater is corrosive because it contains about 3.5% salt. In addition, some of the biological pollution in the sea also accelerated the corrosion of the sea water. Titanium is a kind of material with excellent physical properties and stable chemical properties. Titanium and its alloys have high strength, small specific gravity, corrosion resistance to seawater and ocean atmosphere, which can meet the requirements of people in ocean engineering. After years of hard work by titanium industry professionals and researchers in the field of marine engineering applications, titanium has been widely used in many fields, such as offshore oil and gas development, harbor construction, coastal power station, seawater desalination, ships, marine fishery and ocean heat energy conversion. Now, titanium for Marine engineering has become one of the main fields of titanium in civil application. 2.1 The development of offshore oil and gas is the economic lifeline of a country. It is estimated that the world has 300 billion tons of recoverable oil reserves, of which about 130 billion tons are on the seabed. The exploitation of offshore oil began in the early 20th century. Its development has experienced from near sea to far sea and from shallow sea to deep sea. Limited by technical conditions and material development, only oil and gas deposits extending directly from the coast to the shallow sea can be exploited initially. Since the 1980s, stimulated by the energy crisis and technological progress, offshore oil exploration and development have developed rapidly, and offshore oil development has advanced rapidly to the continental shelf, gradually forming a new offshore oil industry sector. Offshore drilling platform is a working base for offshore oil and gas exploration and exploitation, which indicates the level of offshore oil and gas development technology. Offshore oil production equipment mainly includes oil production platform and ancillary equipment, such as crude oil cooler, riser, pump, Valve, joint and fixture. These devices are in contact with sulphides, ammonia, chlorine and other media in sea water and crude oil. Because of the excellent corrosion resistance of titanium in these media, the United States in the early 1970s in its oil field using the offshore oil platform pillars made of titanium, at the same time made of titanium tube heat exchanger and plate heat exchanger. Titanium tube heat exchangers use seawater as a cooling medium to cool the hot steam/oil mixture pumped from the well. The titanium plate heat exchanger also uses seawater as cooling medium to cool the crude oil in the carbon steel heat exchanger. The United States employs about 100 titanium heat exchangers on the North Sea oil platforms. The titanium parts ordered by Alberding in Scotland are said to be the world’s first titanium high-pressure riser shaft for the Heidrum Project in Conoco Norway. The service life of petroleum titanium alloy drilling pipe is longer, its weight is only half of stainless steel, but the service flexibility is twice of stainless steel, service life is 10 times of steel. These properties make titanium an excellent material for drilling difficult, nearly circular, deep oil wells. The combined drilling tool including titanium drill pipe can greatly reduce drilling time and total drilling cost. Titanium drill pipes were first used in industrial applications in 2000 by GRANTPRIDECO, RTI energy systems and Torch drilling services of the United States. Titanium drill pipes manufactured and supplied jointly by GRANTPRIDECO and RTI energy systems are also fitted with steel tool joints supplied by Grantprideco anti-fatigue. The utility model has the advantages of light weight, good use flexibility and can make the titanium drilling pipe firm and strong.

It is reported that in the North Sea oil field development project of the United States, the amount of titanium used in the floating body device on the ship and the submarine fixed device is higher than before. The requirements for titanium materials for 24 floating body devices and 64 bottom fixing devices on ships are: 50 ~ 100 T for safety protection device, 50 ~ 100 t for connecting device, 400 ~ 1000 T for general lifting equipment and 1400 ~ 4200 T for drill pipe. The corrosion of structural parts caused by biological pollution of offshore oil platform is very serious. An American company used long casing made of titanium pipe to protect the parts on the platform. The use of titanium alloy components in oil drilling and coastal production operations has increased significantly in the past few years. Titanium-alloy parts allow oil drilling into deeper waters and wells, including higher temperatures and a highly corrosive (or salty) production environment. For such applications, TC4 Titanium Rod (Ti-6Al-4V)-based alloy is the most suitable and the lowest cost in terms of comprehensive properties. Due to its high corrosion resistance to sea water, the service life of the system is 10 times that of the steel system. Therefore, the cost of the system is reasonable compared with that of the Cu-Ni system. Active metals and precision Tube Technologies co-founded a titanium tube technology company to produce a large-bore titanium alloy tube. The pipe is made of TA18(ti-3al-2.5 v) alloy with a diameter of 650 mm, a wall thickness of 22-25 mm, a length of 350 m and a pipe weight of 80-90 t, and is intended for use in offshore oil exploration. Another American company has produced nearly 500m long shaft tubes by extrusion using seamless titanium alloy tubes with a length of 15m, an outer diameter of 600mm and a wall thickness of 25mm, which have been used on an offshore drilling platform. It is claimed that the weight of the Silo Tube can be reduced by half, thus greatly reducing the cost of ballast, in addition to its high fracture toughness and long fatigue life. Practice has proved that Ti-6Al-4V (Gr. 5) alloy is the best material for drilling pipe. As drilling application, yield strength and fatigue strength are the most important, two particularly low gap elements GR.5 alloys are suitable for more critical dynamic lifting devices. When the service temperature exceeds 75 ~ 80 °C, GR29 alloy containing ruthenium is used to prevent crevice corrosion or stress corrosion. The most commonly used components include offshore drilling hoists, drill pipes, cone-shaped stress connectors (TSJ) , and titanium/steel hybrid hoists. Titanium pumps, valves, joints, fasteners, fixtures and spare parts and other small titanium components in oil production platforms have been widely used. Titanium Alloy is also widely used in the shell of offshore oil exploration and logging tools abroad. 2.2 there is a layer of oxide film not more than 10nm thick on the surface of the titanium material of the harbour building. It is very stable in corrosive environment and has excellent corrosion resistance to air, sea water and marine environment, is currently the most suitable for all kinds of marine environment of raw materials. Japan has made great efforts to develop the sea, such as the benzhou-shikoku bridge, the Gulf of Tonkin Bridge across the road, the Kansai International Airport, the floating oil storage base and so on. The exposure tests carried out by the Japanese Construction Ministry and the Iron and Steel Club on the sea surface of ōi River, as well as various corrosion exposure tests carried out by the Ministry of Transport and the Association of Steel Pipe Piles on the pozaki drift sand trestle bridge, also show that titanium is the most suitable material. In addition to its excellent corrosion resistance, titanium has the advantages of little dissolved ions in seawater, no toxicity, no pollution and so on. Japan has also built a super-large floating marine structure, using titanium steel composites where the water has scoured it, and has used titanium as a splash-proof torso for piers across the Gulf of Tonkin highway, each of which uses 0.9 t of titanium. Large floating marine structures in use or planned are airports, harbor logistics bases, sports facilities, and so on. 2.3 The comprehensive utilization of sea water in coastal power stations is one of the important projects in ocean engineering. Titanium used in coastal power stations is mainly used in condensers. Since the condenser uses seawater as cooling water, and seawater contains a lot of mud and sand, suspended matter, marine organisms and various corrosive substances, the situation is more serious in the seawater and river water alternating fresh salt water. The traditional condenser is made of copper alloy tube, which is often damaged seriously because of various corrosion in seawater. Titanium has good corrosion resistance in seawater, especially in polluted seawater, especially in high-speed erosion corrosion resistance. 2.4 Desalination Plant “Water is the source of life”. At present, the lack of water resources has become a problem plaguing the whole world. About 25 per cent of the world’s population does not have adequate drinking water resources. The land rivers and groundwater resources in the world can not meet the needs of industrial development. Therefore, seawater desalination will be an effective way to solve the problem of freshwater resources. From the development of seawater desalination at home and abroad, there are mainly two methods: distillation and reverse osmosis. In the former, seawater is heated to vaporize it, and then steam is condensed to produce fresh water. The latter is the sea water pressure, so that the fresh water through a special membrane and salt interception of fresh water. The early seawater desalination devices used copper alloy, carbon steel and other materials, because these materials are not resistant to seawater corrosion, low production efficiency, quickly seawater corrosion resistance excellent titanium replaced. In seawater desalination, the main application of titanium is the heater heat transfer tube. The main producers of desalination units are the United States and Japan. By 2004, more than 15,000 desalination plants had been built or under construction worldwide, with a daily output of about 32 million tons of fresh water. The Japanese company built 10 distillation units with a daily production of 30,000 tons of fresh water for Saudi Arabia, using 3,200 tons of titanium tubes and an average daily production of 10,000 tons, requiring 107 tons of titanium. Seawater desalination units have been or are being built in Tianjin, Shandong and other places. For example, the initial plan for seawater desalination in Tianjin is to produce 500,000 tons of fresh water per day by 2007 and 700,000 tons by 2010. Seawater desalination projects in Tianjin and Shandong are expected to use about 250 tons of titanium.

Ocean engineering, as a new civil market of titanium, has been developing rapidly in recent years. With the deepening of the world energy crisis, the countries of the world will invest a lot of human and material resources to exploit the seabed oil resources and other mineral resources, every coastal country will use seawater to make fresh water, moreover, each military power’s naval equipment competition day by day and so on, these all can not leave titanium and the titanium alloy material. Therefore, titanium and its alloys will be more and more widely used in ocean engineering. It is expected that titanium for offshore engineering will become a large application market of titanium materials. Current market situation at present, iron, aluminum and stainless steel are widely used in tableware and cookware materials at home and abroad, in the use of the human body are more or less conducive to health factors: 1 Iron Pot: to the food of iron, is trivalent iron, the human body is not absorbed, the human body can only absorb bivalent iron. 2 Aluminum Pot: in high temperature acid, alkali conditions will have aluminum leaching, causing aluminum poisoning, is not safe. The International Health Organization expressly prohibits the use of aluminium pans in contact with foods containing salt. 3 nonstick pans: Most are made with “Teflon”paint, which the US government has accused of being a carcinogen. Teflon releases more than a dozen harmful gases at high temperatures, killing some animals with sensitive airways. But the toxic effects of these gases on humans have not been determined. 4 enamelware: the Enamel coating is actually a layer of enamel, containing a substance such as aluminum silicate. Because of the impact of friction stir-fry, easy to cause damage, so that aluminum silicate and other substances will be transferred to the food. Pottery Pot, casserole: the potential harm mainly has two aspects: one is the soil casserole enamel, the other is “Pseudo purple sand.”. “Pseudo purple sand”added iron powder, manganese dioxide and other chemical pigments prepared from processing, made of chemical agents to enhance color, rather than real purple sand. 2. Titanium health products advantage titanium health products advantage is in titanium metal surface has a solid layer of titanium oxide compound film, chemical property extremely stable, and even acid in the “Aqua regia”can not defeat it. The Titanium Pot does not react with the ingredients when cooking. So can cook the raw materials of the original flavor, pure titanium pot is the only can be used to fry Chinese medicine metal pot. In the United States and Japan, titanium pot is called delicious pot, the original flavor of delicious is healthy elements. The heat function of titanium pot is excellent: can be low-temperature, fast, low-fat cooking out of green dishes, maximum retention of ingredients and taste. Green food with high nutrition is a healthy element. The use of titanium tableware, cookware advantages reflected in the following aspects: 1) strong anti-corrosion: Corrosion than stainless steel, even the most corrosive package of “Aqua regia”(a mixture of concentrated sulfuric acid and concentrated nitric acid) also have no rust, long-term cooking and storage of acidic and alkaline food will not produce metal smell, can also be used to cook Chinese medicine. Pots made of other metals can not do this. High hardness: Much higher than the hardness of stainless steel, abrasion resistance, scratch resistance, semi-permanent use. Light Weight: Easy to use by your wife. It weighs half as much as a wok and is light to use. Do not need to maintain: The husband use is very assured, high temperature burn not bad, not broken, do not need maintenance. Antibacterial: with natural photocatalyst antibacterial effect, in natural light with natural antibacterial effect, health, no bacterial pollution. Non-stick effect: Good non-stick effect, and pot equivalent, but not completely non-stick. Energy Saving: Save Time and energy, heat transfer speed is 7 times of the Iron Pot, is the composite bottom steel pot and alloy pot dozens of times, cooking energy saving. BIOCOMPATIBILITY: is the human body affinity metal contact for a long time will not be allergic, medical has replaced stainless steel as a “Human bone”implanted in the body. Health: 99.75% pure titanium is made without coating, it is the healthiest and safest metal pot. Non-stick surface: Electrolytic grinding more comprehensive and thorough, there is no residual mechanical polishing of harmful dust particles, electrolytic grinding of titanium pan with a fine concave-convex surface, can improve heat transfer speed and non-stick. In the eyes of the public, titanium is used to make luxury goods such as space shuttles, nuclear reactors, jewelry and golf clubs for the eyes. Titanium has such wonderful properties, and it’s also a very difficult metal to work with. The understanding of titanium processing technology and processing means restricts the relevant enterprises to enter this field. Up to now, domestic titanium tableware and cookware is still a virgin land, waiting for the development of people with insight. The titanium tableware and cookware produced by this project overcome the artistic difficulty and aesthetic stereotype of pure titanium metal, and have bright colors, making the perfect combination of science and technology with living technology. So that millions of households really experience”to health, WITH TITANIUM POT!”!

Research progress in titanium alloys for aviation titanium elements are widely distributed, containing more than 0.4% of the earth’s crust mass, and the global proved reserves are about 3.4 billion tons, it ranks 10th in all elements (oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium, hydrogen, titanium) . Titanium was first obtained by the “Sodium method”(sodium reduction of TICL4) by American scientists in 1910, but the titanium industry did not develop immediately with the discovery of titanium. It wasn’t until 1948, after World War II, that the titanium industry took off in the United States with the invention of the “Magnesium process”(magnesium reduction TiCl4) by scientists in Luxembourg. Titanium is 40% less dense than steel, and its strength is comparable to that of steel, which can improve structural efficiency. At the same time, titanium has good heat resistance, corrosion resistance, elasticity, anti-elasticity and formability. Because of these properties, titanium is used in the aviation industry from the very beginning. In 1953, titanium was used for the first time in the DC-T engine firewalls and Nacelles produced by the Douglas, and titanium began to be used in aviation. The space shuttle is the most important and widely used aircraft. Titanium is the main structural material of aircraft, as well as the preferred material for important components such as aeroengine fans, compressor disks and blades. It is known as “Space metal”. The more advanced the aircraft, the more titanium consumption, such as the United States F22 fourth-generation aircraft titanium content of 41% (mass fraction) , its F119 engine titanium content of 39% , is currently the highest content of titanium aircraft. The research of titanium alloys originated from aviation, and the development of aviation industry has promoted the development of titanium alloys. The research of Aviation Titanium Alloy is always the most important and active branch in the field of titanium alloy, but its development is also extremely difficult, for example, people spend more than ten years to overcome the “Thermal barrier”problem of aviation engine titanium alloy. In this paper, titanium alloys are classified according to their matrix phase composition. The application and research of Titanium Alloy in aero-engine, airframe and aviation fastener are introduced. Finally, the problems existing in the development of titanium alloys for aviation are analyzed. 1 Titanium Alloy classification of the United States, the United Kingdom, Russia, France, Japan and other countries titanium alloy classification for their own manufacturers, a wide range of names. Some companies directly use chemical symbols and numbers of elements instead of alloy elements and their content naming, such as Ti-6Al-4V (equivalent to TC4 in China) , national brand comparison and chemical composition as listed in Table 1. According to the phase composition, titanium alloys can be divided into α type titanium alloys (including near α type alloys) with closely spaced hexagonal structure (HCP) , I. E. Domestic Grade TA and two phase mixed α + β type titanium alloys, I. E. DOMESTIC GRADE TC and body centered cubic structure (BCC) type β type titanium alloys (

1. The single-phase solid solution alloy with α-titanium as Matrix during annealing is α-titanium alloy, which mainly contains Al, Sn and so on. Al Is an important alloying element in titanium alloys, which can increase the tensile and creep strength, decrease the density and increase the specific strength of titanium alloys. In order to maximize the solid solution strengthening effect of aluminum and avoid the embrittlement of alloy caused by excessive Al, the alloying of high temperature titanium alloy should follow the equivalent empirical formula proposed by Rosenberg, only in this way can we ensure that the alloy can improve the heat resistance strength while maintaining good thermal stability. These elements play a stabilizing role in α-titanium alloy by suppressing the phase transformation at phase transformation temperature or increasing the phase transformation temperature. Compared with β type titanium alloy, α type titanium alloy has good creep resistance, strength, weldability and toughness, so it is the first choice for high temperature use. At the same time, α-type alloy has no cold Brittleness, it is also suitable for use in low temperature environment, expanding its application range. The forging defects can be controlled by reducing the processing rate per pass and frequent heat treatment. The α Matrix is a stable phase. For a given composition alloy, the change of properties is mainly the change of grain size, because the yield strength and creep resistance are related to the grain size and the energy stored during deformation. The strength of α-type titanium alloy can not be improved by heat treatment, and there is little or no change in the strength after annealing. Some alloys contain more AL, SN, Zr and a small amount of β stable elements (generally less than 2%) . Although these alloys contain β phase, the Matrix is mainly composed of α phase, which is similar to α type alloy in heat treatment sensitivity and machinability, and is called near α type titanium alloy. The development of near α alloys is based on the recognition that high creep strength can be obtained by strengthening α matrix with solid solution alloying elements, now it has become an important alloy type of high temperature titanium alloy. The strengthening mechanism is that the atom in β phase diffuses quickly, and it is easy to creep, and the β stable element also inhibits the embrittlement of α phase (that is, retards the formation of ordered phase in α) . The common α-type titanium alloys (including near-α-type alloys) include TI811(TI-8AL-1MO-1V) , Ti-6Al-2Zr-1Mo-1V, Ti-679(Ti-2.25Al-11Sn-5Zr-1Mo-0.25SI) , BT18(Ti-7.7Al-11Zr-0.6Mo-1Nb-0.3SI) and Ti6242S (Ti-6Al-2Sn-4Zr-2Mo-0.1SI) . Their compositions and properties are listed in Table 2. 1.2 α + β titanium alloy to improve the strength and toughness of titanium alloy, α + β titanium alloy has been developed. Compared with other titanium alloys, α and β phases are strengthened by adding both α and β stable elements in α + β alloys. α + β Alloy has excellent comprehensive properties, such as its strength at room temperature is higher than that of α alloy, its hot working property is good, and it can be strengthened by heat treatment, so it is suitable for aeronautical structural parts. The annealed microstructure of α + β Titanium Alloy is α + β phase, and the content of β phase is generally 5% ~ 40% . However, the microstructure of the alloy is not stable enough, the service temperature can only reach to 500 °C, and the weldability and heat resistance of the alloy are lower than those of α-type titanium alloy. α + β titanium alloys mainly consist of TC4(ti-6al-4v) and tc-6(ti-6al-1. 5cr-2.5 mo-0.5 fe-0.3 SI) , TC11(ti-6.5 al-3.5 mo-1.5 zr-0.3 SI) , TC17(TI-5AL-2SN-2ZR-4MO-4CR) , TC19(Ti-6Al-2Sn-4Zr-6Mo) and TC21(ti-6.2 al-2.8 mo-2nb-2sn-2.1-1.3 CR) . TC11 alloy is also called near β alloy. A new microstructure of TC11 alloy was obtained by heat treatment at 15 ° below the β-transformation temperature, followed by rapid water cooling and high and low temperature toughening and strengthening heat treatment. The Matrix consists of 15% equiaxed α grain, 50% ~ 60% lamellar α grain and transformed β grain. The results show that the alloy exhibits high fatigue resistance, long creep fatigue life, high toughness and excellent high temperature service performance, and does not reduce the plasticity and thermal stability.

The new process and the experimental principle of strengthening and toughening mechanism are also discussed. The key problem of the practical application of the process is the accurate control of the temperature. The TC11 titanium alloy processing technology has been applied to produce reliable aero-engine compressor disks, rotors and other components. 1.3β titanium alloy is called β titanium alloy, which has high content of β stable element and rapidly cooling β phase after solution treatment to room temperature. β Titanium alloys can be classified into stable β titanium alloys and metastable β titanium alloys, as shown in Fig. 1. In Fig. 1, MS is the MARTENSITIC transformation temperature line, βc is the lowest content of β stable element in metastable alloy, βs is the lowest content of β stable element in stable alloy.

β Alloy has good cold formability in solution state, and its hardenability and heat treatment response are also excellent. The commonly used heat treatment method is solution treatment first, then aging at 450 ~ 650 °C, fine α phase will be precipitated on the original β Matrix, forming the dispersion distribution of the second phase, which is the strengthening mechanism of β alloy. β Titanium Alloy has the highest strength at room temperature because β titanium alloy precipitates more α phase and contains more α-β phase than other titanium alloys. The ability of metal materials to absorb energy during deformation and fracture is called toughness. The more energy a material absorbs, the better its toughness. Fracture toughness is an index of material toughness, which reflects the resistance of material to crack and other sharp defects. Generally speaking, the fracture toughness and strength of titanium alloy show an inverse ratio trend, I. E. The increase of strength and the decrease of fracture toughness. In order to study the application of β titanium alloy in aerospace industry, it is necessary to design the microstructure, processing technology and heat treatment system with good strength and fracture toughness. The composition and microstructure of the alloy are the two main factors that determine the fracture toughness of β titanium alloy. The alloy composition determines the amount of β phase in the alloy, as well as the alloy type and fracture toughness. The morphology, quantity and volume of microstructure also affect the fracture toughness. Fu Yanyan and others think that β stable element and Zr can increase the strength and decrease the fracture toughness of β titanium alloy. The small β grains can not effectively improve the strength of aged β titanium alloy, and can decrease the fracture toughness of Ti-15-3 alloy, but have no obvious effect on the fracture toughness of Β-C and Ti-1023 alloys. The strength of aged β titanium alloy depends mainly on the content and size of the secondary α phase precipitated during aging. The Fine Secondary α phase can significantly increase the strength of the alloy. The coarsening of primary α phase and the transformation of primary α phase from spherical to flaky can lead to the decrease of plasticity and the increase of fracture toughness of β titanium alloy. The two-state microstructure of β titanium alloy has good matching of strength, plasticity and toughness. β Titanium alloys have been widely used because of their high strength and high plasticity that other types of titanium alloys can not match. At the same time, β titanium alloy has been gradually replaced by α + β two-phase titanium alloy as the preferred structural material for airframe and wing because of its heat treatment strengthening and deep quenching ability, is playing an increasingly important role in the aerospace industry. The development and application of aviation titanium alloy in the 1950s, the military aircraft entered the supersonic age, the original aluminum, steel structure can not meet the new demand, titanium alloy just at this time into the industrial development stage. Due to its low density, high specific strength, corrosion resistance, high temperature resistance, non-magnetic, weldable, wide temperature range (269 ~ 600 °C) and other excellent properties, titanium alloys are capable of forming, welding and machining various parts, in the field of aviation soon to be widely used. In the early 1950s, military aircraft began to use industrial pure titanium after the body of the Heat Shield, tail cover, speed plate and other structural components under less force. In the 1960s, titanium alloy was further used in the slip-rolling of aircraft flap, load-bearing frame, Middle Wing box girder and landing gear girder. By the 1970s, the application of titanium alloy in aircraft structure was extended from fighter plane to military large bomber and transport plane. Since the 1980s, titanium for civil aircraft has gradually increased, and has already surpassed titanium for military aircraft. The more advanced the plane, the more titanium it takes. Table 3-5 shows the mass fraction of titanium used in the 3rd and 4th generation fighters, advanced bombers and transport aircraft, the types of titanium alloys used in general aircraft and the amount of titanium alloys and composites used in Airbus aircraft. As can be seen from table 5, the use of titanium on Airbus A380 aircraft has reached 10% , titanium has become an indispensable structural material of modern aircraft. According to different uses, aviation titanium alloy can be divided into aircraft engine titanium alloy, aircraft body titanium alloy and aviation fasteners titanium alloy. In recent years, the application of aviation titanium alloy in the above three aspects has been deeply studied.

2.1 titanium engines for aircraft engines are the heart of aircraft. Engine Fan, high-pressure compressor disk and blades and other rotating parts, not only to bear a lot of stress, but also to have a certain degree of heat resistance. Such conditions are too hot for aluminium and too dense for steel. Titanium is the best choice. Titanium has good high temperature strength, CREEP RESISTANCE AND OXIDATION RESISTANCE AT 300 ~ 650 °C. At the same time, an important performance index of the engine is the thrust-to-weight ratio, i. e. the ratio of the thrust produced by the engine to its mass. The thrust-to-weight ratio of the original engine is 2 ~ 3, now it can reach 10. The higher the thrust-to-weight ratio, the better the engine performance. The use of titanium alloy instead of the original nickel-base superalloy can reduce the engine quality and greatly increase the thrust-weight ratio of aircraft engine. Titanium is increasingly being used in aircraft engines. In foreign advanced aero-engines, the amount of high temperature titanium alloy has accounted for 25% ~ 40% of the total engine mass, such as 25% for F100 and 40% for F119. Aeroengine components require titanium alloys to have good transient strength, heat resistance, endurance strength, high temperature creep resistance and structural stability in the temperature range from room temperature to high temperature. Although β and near β titanium alloys have high tensile strength from room temperature to about 300 °C, the creep resistance and thermal stability of the alloys decrease rapidly at higher temperatures, so β titanium alloys are rarely used in aircraft engines. α-type and near-α-type titanium alloys have good creep, durability and weldability, and are suitable for high temperature applications. α + β titanium alloy not only has good hot working properties, but also has good comprehensive properties in medium and high temperature environment. Therefore, α, near α and α + β titanium alloys are widely used in aero-engines. Titanium alloys for aircraft engines developed worldwide are listed in Table 6. At present, the highest working temperature of high temperature titanium alloy used in aeroengine has been raised from 350 °C to 600 °C, which can meet the requirement of advanced engine. After half a century of efforts by titanium alloy researchers around the world, sentence is too long, please supply a shorter sentence. TI811(TI-8AL-1MO-1V) alloy has many advantages, such as low density, high elastic modulus, excellent vibration damping property, good thermal stability, good weldability and formability, etc. . Zhao Yongqing et AL studied the thermal stability and high temperature fatigue property of TI811 alloy, and studied the effect of microstructure and surface state of samples on the thermal stability of TI811 alloy. The results show that the TI811 alloy with equiaxed structure and dual-state structure has good thermal stability, and the presence of acicular structure deteriorates the thermal stability of TI811 alloy. In addition, the results show that the surface oxidation layer and exposure time have no obvious effect on the thermal stability of TI811 alloy exposed at 425 °C. The Effects of temperature, displacement amplitude and contact pressure on the high temperature fretting fatigue (FF) behavior of TI811 titanium alloy were investigated by using high frequency fatigue tester and home-made fretting fatigue apparatus. The results show that the fretting fatigue sensitivity of TI811 alloy increases with the increase of temperature at 350 °C and 500 °C, and creep is an important factor for the failure of TI811 alloy FF at high temperature, the change of displacement amplitude affects the role and mechanism of fatigue stress and wear in FF process. Ti-6Al-2Zr-1Mo-1V is a universal alloy developed by the former Soviet Union in the 1960s. The alloy can work at 300 ~ 500 °C and is mainly used to produce aircraft engine case. Ouyang et Al have done a lot of work on the recrystallization behavior of Ti-6Al-2Zr-1Mo-1V titanium alloy at different temperatures and strain rates. The results show that when the deformation temperature is higher than 1050 °C and the strain rate is lower than 0.01 s-1, the dynamic recrystallization mechanism is mainly discontinuous dynamic recrystallization, and when the deformation temperature is lower than 1050 °c and the strain rate is higher than 0.01 s-1, the dynamic recrystallization mechanism of the alloy is mainly continuous dynamic recrystallization with a small amount of discontinuous dynamic recrystallization. In addition, the phase transformation orientation of Ti-6Al-2Zr-1Mo-1V alloy is different from that of other titanium alloys. The results show that the transformation of external factors (such as deformation stress, strain rate and cooling rate) follows the potential-to-direction transformation rule in the stage of β → α. However, strain rate and cooling rate can significantly affect the morphology of α precipitation phase. Ti-679 alloy is made of low aluminum and high tin, and the alloy elements such as Zr, Mo and SI are added to it. It can be used as engine high pressure compressor blade and disk. In its alloy elements, the role of aluminum is to increase the strength of the alloy, but easy to lead to poor plastic deformation, with low aluminum and high tin, you can get better shape and strength; The function of zirconium is to supplement and strengthen α phase. The creep resistance and thermal stability of Ti-679 alloy are good, and its working temperature can reach 450 °C.

3. Existing problems and prospects titanium is a kind of metal with excellent properties and rich reserves, which is called “Modern metal”. After half a century of development, great progress has been made in the preparation technology and application research of titanium alloys, it is especially widely used in the field of aviation. However, some problems have been exposed gradually, and the further development of aviation titanium alloys is facing great challenges, mainly in the following three aspects: (1) dosage. Whether military or civilian aircraft or aircraft, titanium alloy levels directly reflect the level of a country’s aviation. At present, the titanium consumption of aeroengine is low, and it is still very difficult to increase to about 50% . (2) performance. As other aeronautical structural materials, high performance is required to have a good performance match, that is, must comprehensively consider its mechanical properties, physical properties, chemical properties, process properties and defects controllability. The creep resistance and high temperature oxidation resistance of existing titanium alloys are the two main obstacles to the expansion of titanium alloys. The author thinks that in the whole process of development and application of aviation titanium alloy technology, new manufacturing technology will be the focus of development and research, such as superplastic forming and Powder metallurgy forming. (3) cost. At present, people have made some achievements in reducing the cost of aviation titanium alloy, but there are still many fields to be researched and developed. Taking flame-retardant Titanium Alloy as an example, Alloy-C invented in the United States, although it has excellent flame-retardant properties and high-temperature mechanical properties, but it needs to add a lot of expensive V and poor forgeability, which leads to high price, therefore, only in the F119 engine in the official application. Because of the backward management and technology, the price of domestic titanium alloy products is not competitive in the world, which is not conducive to further expanding the application in China. Therefore, first of all, we must seriously study ways to reduce the cost of titanium products, determine the near, medium and long-term development planning. Secondly, China should establish its own titanium alloy system to ensure a variety of alloy options for each use, gradually get rid of the long-term dependence of aviation key materials on foreign countries, and form trunk materials or general-purpose materials, it lays the foundation for realizing low-cost manufacturing. Finally, it is an important task to replace the precious alloy elements with the elements with lower price and reduce the cost of titanium alloy parts by technological means. To sum up, titanium alloy is a kind of aviation material with high thrust-weight ratio, high toughness, good strength and weldability. In the past several decades, the alloying theory, comprehensive strengthening and toughening technology and heat treatment technology of aviation titanium alloys have been greatly developed. At present, the research of titanium alloys mainly focuses on the thermal stability, creep resistance and low-cost titanium alloy design and manufacturing process. With the development of the research, the technology of low-cost machining of titanium alloy will be driven by the high-end application of aviation, and the cost bottleneck restricting the quantity and application level of aviation titanium alloy will be broken. All Titanium aircraft may be a reality in the not too distant future. 

Source: Caitong