Manufacturing, petrochemical and many other aspects. In the application, the aviation industry takes the first place. Taking the US F-15 as an example, it is mainly used to make wings, horizontal tails, vertical tails, landing gear and air intakes. In addition, structural titanium alloys can also be used as wing skeletons, bases, engine compartments, etc., and their applications in oil pipes, rivets, and fasteners are also increasing. It is mainly used in aerospace engineering as pressure vessels (storage of compressed air or liquid propellants), star and arrow connection belts, solid engine casings, various skins, components and radiation-cooled nozzles. For ships, the former Soviet Union built a nuclear-powered attack submarine with an all-titanium shell in 1970, and later built four, each with a titanium alloy of 3500t. In 1982, it was made into a Typhoon titanium-shell core submarine, each of which used a 9000t titanium alloy. This breaks the situation where titanium is limited to torpedo launchers and deep submersibles. Structural titanium alloys are not used on conventional weapons, and are mainly used for artillery, firearms and other auxiliary equipment.

Since the 1960s, titanium alloys have been used in the shipbuilding industry. The former Soviet Union and the United States both have their own series of marine titanium alloys, such as the former Soviet Union's 48-T series titanium alloys, 48-T2, 48-T3, 48-T4, 48-T5, 48-T7, etc .; American marine titanium alloys There are: Ti—5Al—2.5Sn, Ti—6Al—4V, Ti—6Al—6V—2Sn, Ti—8Al—1Mo—1V and Ti—6Al—2Nb—1Ta—0.8Mo, etc .; Chinese marine titanium alloys start at 60 At the end of the decade, the amount was small and did not form its own marine titanium alloy series. To meet the needs of designers, structural titanium alloys are classified by strength. According to the requirements for the use of materials, when selecting the structural titanium alloy grade, factors such as the required strength, forming type, corrosion resistance, weldability, and cost must be considered. According to strength, it can be divided into low strength (<750MPa), medium strength (750 ～ 1000MPa) and high strength (> 1000MPa). The table lists the most common structural titanium alloys with various strength ranges.

In low-strength structural titanium alloys, Ti-3Al-2. 5V and Ti-2A1-1.5Mn are the practical ones. Among the medium-strength structural titanium alloys, Ti-5Al-4V and Ti-6Al-4V are the practical ones. Ti-6Al-4V alloy is the most widely used, and the amount is the largest. When a medium-strength alloy plate is required, Ti-5Al-4V is selected, but the cold forming performance is poor, and hot forming is required. High-strength structural titanium alloy is suitable for making large-section forgings, such as front wing beams, longitudinal beams, landing gear, and so on. These parts require comprehensive properties such as high strength, high toughness, and high hardenability. Therefore, α + β high-strength alloys with high β-stabilizing elements and near-β high-strength alloys have been developed.

Because α + β-type titanium alloys have poor fracture toughness and small hardenable depth under high-strength state, people's attention is focused on developing β and near β-type titanium alloys. The characteristics of the near β-type titanium alloy are: it has the high strength, high toughness, and high hardenability of the metastable β-type titanium alloy, and it also has the tensile ductility and elastic modulus of the α + β-type titanium alloy. It has the characteristics of low thermal deformation temperature and low thermal deformation resistance. The high strength, high toughness and high hardenability of this type of alloy improve the structural efficiency and reliability of structural parts. The beta and near beta alloys developed in the early days are:

(1) Ti-13V-11Cr-3Al, Ti-11.5Mo-6Zr-4.5Sn (βⅢ) and Ti-3Al-8V-6Cr-4Mo-4Zr (βC) in the United States.

(2) Ti-3Al-7Mo-11Cr, Ti-3Al-5Mo-6V-11Cr and Ti-2Al-8.5Mo-8.5V-1.2Fe-1.2Cr, etc. in the former Soviet Union.

(3) China's Ti-5Mo-5V-8Cr-3Al, Ti-10Mo-8V-1Fe-3.5Al, and Ti-4Al-7Mo-2Fe-1Zr, etc. From the 1970s to the 1990s, various countries mainly researched and developed Ti-10V-2Fe-3Al, Ti-15V-3Al-3CI-3Sn, Ti-5Mo-5V-2Cr-3Al, and Ti-5A1-5Mo-5V-1Fe-1Cr, etc. . Except Ti—15V—3Al—3Cr—3Sn as sheet alloy, the other three alloys are forging alloys.

 A titanium alloy used as a load-bearing member at normal temperature (-60 to 400 ° C). It was mainly developed to meet the needs of aircraft body structural parts, and then expanded to applications in rockets, satellites, weapons and ships. The application on aircraft body structural parts began around 1950 and has developed rapidly in 50 years. The third-generation American supersonic fighters F-14, F-15 and Phantom-2000 titanium alloys account for 20% to 25% of the body structure. The titanium alloy on the F-22 fighter of the new generation of American aircraft accounts for 31% of the structural weight. China's use of titanium alloys on fighter airframes was in the 1960s. In 1983, TC4 titanium alloy die forgings were used for important structural parts of aircraft. The new models designed in the 1990s used titanium alloy grades such as TA6, TA7, TC1, TC3, TC4, TC6, TC11, ZT3 and ZT4.