How much titanium alloy accounts for the alloy material on the aircraft?



The alloy materials on the aircraft mainly include aluminum alloys, magnesium alloys, and titanium alloys, among which aluminum alloy materials account for about 50%--70% of aircraft materials, and magnesium alloy materials account for about 5%--10% of aircraft materials. For aircraft, the proportion of titanium alloys is increasing.

1. Aluminum alloy

Aluminum is a light metal with low density, high plasticity and easy processing. It can be made into various profiles and plates with good corrosion resistance.

Aluminum alloy has a series of advantages such as low density, high specific strength, good corrosion resistance and formability, and low cost. It has broad application prospects and irreplaceable status in aviation, aerospace, shipbuilding, nuclear industry and weapon industry.

In aviation, aluminum alloy is the main material for aircraft body structure.

In the early stage of development, in order to improve the mechanical strength of aluminum alloys, researchers successively developed 2014 and 2017 alloys, and then developed 2024-T3 alloys, Al-Zn-Mg-Cu alloys 7075-T6, and subsequently developed higher strength alloys. The 7178 is a T6 alloy.

However, 2024-T3 and 7075-T6 alloys have the tendency of stress corrosion cracking in the short transverse direction. The stress corrosion problem of 7xxx series aluminum alloys was solved by the successful development of 7075-T73, and then the T76 state, which can meet the requirements of corrosion resistance to a certain extent under the condition of sacrificing less strength, was developed.

In order to improve the fracture toughness of aluminum alloys, the United States first developed the 7475 alloy. In order to further meet the requirements of structural strength and stress corrosion resistance of thick and large sections, Alcoa has developed 705 small T74 alloy.

2. Magnesium alloy

Magnesium alloy has high anti-vibration ability, can absorb large energy when subjected to impact load, and has good heat absorption performance, so it is an ideal material for manufacturing aircraft hubs. Magnesium alloys are also used in some components on missiles and satellites.

At present, the applications of magnesium alloy materials in the aviation field mainly include: aircraft frames, seats, engine cases, gearboxes, etc.

In order to improve the strength of magnesium alloys, researchers have re-examined various Mg-RE alloys in recent years, and systematically studied Mg-Nd-Zn, Mg-Gd, Mg-Gd-Y, Mg-Gd-Nd, etc. A Mg-RE series alloy was studied, and the strengthening and toughening mechanism of the alloy was mainly discussed. It was found that JDM1 and JDM2 magnesium alloys have excellent comprehensive mechanical properties.

JDM1 cast magnesium alloy is a magnesium alloy with low rare earth content. Its typical room temperature mechanical properties are yield strength of 140 MPa, tensile strength of 300 MPa, and elongation of 10%. The typical microstructure is shown in the figure below.

JDM2 cast magnesium alloy is a magnesium alloy with high rare earth content, and its typical room temperature mechanical properties are 240 MPa yield strength, 370 MPa tensile strength, and 4% elongation. The typical microstructure of the alloy is shown in the figure below

Combining advanced magnesium alloy materials with new molding processes, a variety of aerospace components have been prepared:
1) Using the combination of coating transfer precision casting technology and JDM1 casting magnesium alloy, a certain type of light missile cabin and engine case were successfully prepared, which satisfies the high degree of smoothness of the inner surface (non-machined surface) of the cabin and engine case. Require.
2) Using the combination of large-scale casting low-pressure casting technology and JDM2 casting magnesium alloy, a certain type of helicopter tail reduction casing was successfully prepared. These two types of castings are large in size and complex in structure, and it is difficult to avoid casting shrinkage by conventional casting. The above problems have been successfully solved by increasing the holding pressure of low-pressure casting and controlling the solidification temperature field of the casting, and the prepared casting has passed the strict inspection by the user.
3) The JDM2 magnesium alloy was combined with the conventional isothermal hot extrusion process, and a certain type of light missile wing was successfully prepared (Fig. (a)).
4) The JDM1 magnesium alloy was combined with the conventional isothermal hot extrusion process to successfully prepare a φ145 mm seamless tube (Fig. (b)), which was used for the preparation of a certain type of light missile casing.

3. Titanium alloy
Titanium and titanium alloy materials have low density, high specific strength (the highest among metal materials at present), corrosion resistance, high temperature resistance, non-magnetic, good microstructure and stability, and can be directly connected to the composite structure, and the thermal expansion between the two The coefficients are similar, it is not easy to produce electrochemical corrosion, and has excellent comprehensive performance. Therefore, titanium alloys are more and more widely used in the aviation field.
In 1950, the United States first used non-load-bearing components such as rear fuselage heat shields, wind deflectors, and tail covers on the F-84 fighter-bomber. Since the 1960s, the use of titanium alloys has shifted from the rear fuselage to the middle fuselage, partially replacing structural steel to manufacture important load-bearing components such as bulkheads, beams, and flap slide rails. The amount of titanium alloys used in military aircraft has increased rapidly, reaching 20% ​​to 25% of the weight of the aircraft structure. Since the 1970s, civil aircraft began to use titanium alloys in large quantities. For example, the amount of titanium used in Boeing 747 passenger aircraft reached more than 3,640 kilograms.
Titanium for aircraft with Mach numbers greater than 2.5 is mainly used to replace steel to reduce structural weight. Another example is the American SR-71 high-altitude and high-speed reconnaissance aircraft (flying Mach 3 and flying height of 26,212 meters), titanium accounts for 93% of the weight of the aircraft structure, and it is known as an "all-titanium" aircraft.

With the continuous development of aviation metal materials, aircraft metal processing technology is also developing rapidly, such as large-scale panel aging forming technology, large-scale die forging manufacturing, 3D printing technology, advanced cementing technology, advanced welding technology, etc.

When designing an aircraft, it is necessary to integrate the advantages of materials, make the best use of the advantages and avoid weaknesses, so as to maximize the performance of the materials, truly realize the safety and efficiency of the aircraft structure, and achieve the purpose of reducing weight, manufacturing and operating costs.