Aircraft engines require the alloy to have good thermal strength and specific strength, while the fuselage requires the alloy to have good strength, corrosion resistance, light weight and other excellent characteristics at moderate temperature. Titanium alloy can well meet these requirements, using titanium alloy as fuselage material has the following five advantages: 1) replace steel and nickel-based superalloy can greatly reduce the quality of the aircraft. The high thrust-to-weight ratio allows titanium alloys to be used in aircraft parts instead of slightly stronger steel. 2) Can meet the requirements of aircraft strength.
Compared with aluminum alloy, about 60% of the mass of titanium alloy can achieve the same strength. Titanium alloys can replace aluminum alloys at temperatures over 130℃, because this temperature is the limit applicable to traditional aluminum alloys. 3) Good corrosion resistance. Most aircraft support mechanisms are under the galleys and toilets, which are prone to corrosion. Titanium alloys do not require surface anticorrosive coatings or coatings. 4) Good electrochemical compatibility with polymer composites. 5) Space limitation, replace steel and aluminum alloy. A classic example of the use of titanium due to space constraints is the titanium landing gear beam of the Boeing 747. This beam is the largest titanium alloy forgings, and although other alloys (such as 7075 aluminum) cost less, the aluminum landing gear is not large enough to meet the requirements when carrying mass is required. Steel is strong enough to carry mass, but it adds a lot to the mass of the aircraft. Figure 2 shows a schematic diagram of the materials used in the fuselage of a Boeing 777. Titanium Beta 21S (Ti-15Mo-3Al-2.7Nb-0.2Si), Ti-10-2-3 (Ti-10V-2Fe-3Al), Ti-15-3 (Ti-15V-3Cr-3Al-3Sn), Ti-3Al-8V-6Cr-4Mo-4 are widely used in aircraft fuselage Zirconium, etc.
The electrode potential of titanium and carbon fiber composites is similar, and titanium alloy is the only connection material of the composite. Therefore, with the increasing of titanium alloy and composite materials used in advanced military and civil aircraft, the demand for titanium alloy fasteners is increasing. Titanium alloy used as aviation fasteners, at least has the following four advantages: 1) good weight reduction effect. A Russian Il-96 aircraft uses 142,000 pieces of fasteners, which can reduce the mass by nearly 600kg. The application of titanium alloy fasteners in Chinese aerospace system also has obvious weight reduction effect. Aircraft and spacecraft with reduced mass can improve thrust, increase range, save fuel, and reduce launch costs.
