Development and application of characteristics of titanium alloys for aerospace

Since the industrialized production of titanium in the 1940s, it has been widely used in aerospace, military industry, marine due to its high strength, good corrosion resistance, non-magnetic, good welding performance and other advantages, as well as superconductivity, memory and other advantages. In the fields of development, petrochemical, power generation, superconductivity, etc., it has the reputation of "Almighty Metal", "Marine Metal", "Third Metal", "Modern Metal" and so on. With the continuous exploration of the excellent properties of titanium, its application scope is still expanding, and it will become the third structural metal after steel and aluminum. In view of the important role of titanium in national defense, aviation, high-tech and other fields, it has been highly valued by the United States, Russia, Britain, France and other military powers and Japan and other countries, and listed as a key structural metal with strategic significance in the 21st century. The development of titanium science and technology, including new alloys, new melting technologies and application technologies, is undergoing rapid changes. China's titanium industry has experienced ups and downs for nearly 40 years. With the support of the state, it has made great progress and established its own independent titanium industry system. In 2000, China produced 1,751 tons of titanium sponge and 2,206 tons of titanium processed materials. In 2008, China produced 49,632 tons of titanium sponge, an increase of 27.3 times in 8 years. In 2008, China produced 27,737 tons of titanium processed materials, an increase of 11.6 times. times.

Due to the high cost of titanium alloy raw materials, 70%-80% of titanium materials abroad are used in the aviation and aerospace industries. The demand for titanium alloys in my country's aviation and aerospace fields is also particularly large. At present, the proportion of titanium alloys used in advanced aircraft under development in my country is about 10%-12%, the proportion of titanium used in military aircraft is higher, about 20%-30%, and the proportion of titanium used in military aircraft engines is more than 30%. . The amount of titanium used in new rockets and missiles is also increasing.

This paper mainly summarizes the progress of research and application of titanium in the aviation and aerospace fields in the United States, Russia, Britain, Japan and China, which can serve as a reference for the application and development of my country's titanium industry in the aviation and aerospace fields.

As the design concept of aircraft gradually changes from pure static strength in the past to safety---lifetime, damage---safety, and until the modern damage tolerance design concept, advanced titanium alloy materials are gradually moving towards high fracture toughness and low crack propagation. Rate of damage-tolerant titanium alloys. At present, foreign developed countries have been at the forefront in the development of new damage-tolerant titanium alloy materials and their application in advanced aircraft, especially such as medium-strength Ti-6Al-4VELI and high-strength Ti-6-222s, etc. It has been successfully used in new generation aircraft such as the American F-22, F-35 and C-17. Greatly improve the service life and combat effectiveness of the aircraft. With the development of aircraft design concepts, the damage tolerance design ideas of titanium alloy structures have also begun to receive attention in my country. Since the "Tenth Five-Year Plan", my country has independently developed TC4-DT medium-strength and high-toughness damage-tolerant titanium alloy and TC21 high-strength and high-toughness damage-tolerant titanium alloy, and established the β machining of damage-tolerant titanium alloy. technology, which has laid the foundation of material application technology for the development of new aircraft in my country. In order to meet the development needs of titanium alloys for aviation and aerospace structures, my country has independently developed low-strength and high-toughness wire titanium alloys (NiTi) and pipe alloys (TA18), 1300MPa-2000Mpa series ultra-high-strength titanium alloys (TB8, TB9, TB20), etc., a new titanium alloy material system with Chinese characteristics for aircraft structures has been initially formed, and a new generation of titanium alloys for aviation and aerospace structures has been established.The specific performance is shown in Table 1

Main technical indicators of typical structural titanium alloys

Ti-6Al-4V (TC4) is a medium-strength α-β titanium alloy developed in the early 1960s. It has excellent comprehensive properties and is known as a universal alloy. It is the earliest and most widely used general-purpose alloy for aviation and aerospace structures. Titanium alloys, including plates, bars and forgings, etc. The alloy has good welding and machinability properties, and the fine-grained alloy has superplasticity, and complex components can be fabricated by the combined process of superplastic forming/diffusion bonding (SPF/DB). High-strength structural titanium alloys generally refer to alloys with a tensile strength of more than 1000MPa. At present, high-strength titanium alloys that represent the international advanced level and have been practically used in aircraft mainly include metastable β-type alloys Ti-15-3, β21S, near β-type alloy Ti-1023 and α-β-type two-phase titanium alloy BT22. Using high-strength structural titanium alloy to replace the 30CrMnSiA high-strength structural steel commonly used in aircraft structures can reduce the weight by more than 20%.

Ti-6Al-2Sn-2Zr-2Cr-2Mo (TC21) is a high-strength, high-toughness, damage-tolerant two-phase titanium alloy developed in the 1970s. After thermomechanical treatment, the alloy has the advantages of high strength, good damage tolerance and excellent resistance to fatigue crack growth, and is suitable for the manufacture of high-strength and high-toughness load-bearing components. By adding Si element, the alloy maintains high strength at medium temperature, which is better than Ti-6Al-4V. The alloy sheet can be superplastically formed at room temperature.

Ti-10V-2Fe-3Al(TB6) is a high-strength, high-toughness near-beta titanium alloy developed in the late 1970s. The alloy has the advantages of high specific strength, good fracture toughness, large hardening area, small anisotropy, good forging performance and strong corrosion resistance, and has many advantages of metastable β titanium alloy without losing α-β titanium alloy. The solid-solution characteristics can meet the requirements of damage tolerance design and high structural efficiency, high reliability and low cost. The maximum working temperature is 320 °C. The main products of this alloy are bars, forgings, thick plates and profiles. Through solution and aging heat treatment, a good match of strength, plasticity and fracture toughness can be achieved, and it is suitable for manufacturing structural parts with high requirements on strength and fracture toughness. Excellent toughness and low crack growth rate can be obtained by thermomechanical treatment, which is suitable for structures with high fracture toughness requirements.