Rapidly Developing Fastener Technology in the US and Russia As the performance requirements for aircraft become increasingly demanding, the performance of fasteners made from ordinary materials has reached its limits. At this point, titanium alloy bolt materials, with their excellent elongation, plasticity, and machinability, have entered the high-end aerospace manufacturing industry. In the 1950s, the United States began using titanium alloy bolt materials in bombers, achieving good results. During the application of these materials, their low density, high strength, and excellent fatigue performance were notable. The alloy composition is very simple, and the cost of semi-finished products is relatively low, leading to widespread use abroad.

Friends who pay attention to the domestic aerospace industry may have noticed a strange phenomenon: in terms of design capabilities, China's domestically produced aircraft and spacecraft are definitely at the world's top tier, but the domestic high-end equipment manufacturing capability is weak and does not match the design capabilities.
It has been nearly ten years since the first flight of the J-20, and the exposed J-20 fleet still consists of only a few aircraft. Apart from the usual discussions about small steps and rapid iterations in design thinking and engine issues, today I will provide another perspective to see how the small component of aviation fasteners has constrained the high-end aviation manufacturing industry for 40 years.

Rapidly developing fastener technology in the US and Russia
As the performance requirements for aircraft become increasingly demanding, the performance of aviation fasteners made from ordinary materials has reached its limit. At this point, titanium alloy bolt materials, with their excellent elongation, plasticity, and cooling processing performance, have entered the high-end aviation manufacturing industry.
In the 1950s, the United States began using titanium alloy bolt materials in bombers, achieving good results. During the application of the material, it has a low density, high strength, and good fatigue performance. The alloy composition is very simple, and the cost of semi-finished products is relatively low, leading to widespread use abroad.

By the mid-20th century, Ti-64 titanium alloy bolts had become widely used fastener materials in the aviation field in the United States and Western European countries. However, due to its low cold working performance, it can only undergo hot processing after forming, requiring vacuum solution equipment for treatment, resulting in high production costs and certain limitations on bolt production sizes. Subsequently, the United States began researching new titanium alloy fasteners.
Russia mainly uses BT16 material in aviation fasteners, which is a high-strength titanium alloy with a high strength level. In practical applications, its production efficiency is much higher than that of Ti-64, and it is widely used in the aviation fastener industry. In recent years, Ti-153, Ti-3553, and other titanium alloys have begun to be used in the aviation field in Europe and the United States, with good application results.

The difficult survival of domestic fastener development
China's research and development of titanium alloy materials for aviation fasteners started relatively late. In the mid-1960s, the Chengdu Aircraft Design Institute began researching TB2 titanium alloy rivet materials, analyzing their application in aircraft fuselages, and only completed the technical identification work by the end of the 1970s.
It wasn't until the 1980s that China began researching TC4 titanium alloy fasteners. After that, China also began to manufacture aviation fasteners using titanium alloys according to advanced foreign experiences. However, due to the instability of quality in China's material production process, there is a heavy reliance on imported materials, which not only increases costs but also leads to insufficient supply in procurement, making it difficult to conduct reasonable research and development.

Taking TC4 material as an example, this material was developed and manufactured by the United States in the mid-20th century and is currently widely used internationally, with a high usage rate. It can be applied in the manufacturing of aircraft landing gear, fasteners, and blades, among other fields, and has very high process plasticity, capable of operating for long periods at 400°C.
Since 2010, China has started a special research and development plan for high-end aviation manufacturing. In the production of aircraft fasteners, TC4 titanium alloy materials have also begun to be used, which can comprehensively improve the strength and performance of bolt fasteners and improve the current production situation.
However, during the application of TC4 titanium alloy materials, cold processing cannot be performed, and only hot treatment measures can be used, which imposes high requirements on process technology.
In this context, it wasn't until around 2019 that China managed to analyze the influence mechanism of heat treatment for TC4 used in aviation, developing heat treatment machine tools for TC4 titanium alloy fasteners, which can effectively carry out industrial production and improve the production level and quality of bolt fasteners.

The pressure on aviation fastener technology comes not only from the backwardness of domestic material science and mechanical processing technology but also from the frightening environment created by foreign suppliers of fasteners, which promotes the idea that 'it's better to buy than to make'.
The main customers of aviation fastener suppliers are aircraft manufacturers and their first-tier suppliers. For example, Boeing has six first-tier suppliers: Alenia Aeronautica (Italy), Subaru Corporation (Japan), Kawasaki Heavy Industries (Japan), Mitsubishi Heavy Industries (Japan), Spirit AeroSystems (USA), and Northrop Grumman (USA). These first-tier suppliers provide 94% of the total fasteners required for Boeing's aircraft production plans.

Due to the large number of Boeing and Airbus aircraft subcontractors in China, materials that were originally restricted due to military supply controls have flooded into the Chinese market.
Taking Xi'an Aircraft Industry Group as an example, it became a major supplier of Boeing aircraft tail wings as early as around 2003, and it is also a major manufacturer of large aircraft in China. A considerable portion of these fasteners, imported under civilian names, has flowed into military aircraft manufacturing processes, which has also reduced the motivation for domestic independent research and development of fasteners.

With the accumulation of high-end manufacturing and materials science, the development of domestic aviation fasteners can actually be described as rapid. In recent years, China has begun to use TC6 titanium alloy materials in the manufacturing of aviation fasteners, which have high-temperature resistance and can operate in environments of up to 500°C.
However, compared to the well-established systems of production, academia, and research, as well as the transformation of research-technology-industrialization abroad, the research and development of domestic fasteners is still extremely reliant on various research institutes fighting their own battles or on national special plans.