High-strength, Corrosion-resistant Aluminum Alloy Materials For Aerospace
With the continuous development of modern aerospace field, nuclear industry and transportation industry, higher requirements are put forward for the comprehensive performance of structural parts, and a new generation of ultra-high strength aluminum alloy with light weight, high strength, high toughness, high fracture toughness and stress corrosion resistance is undoubtedly the first choice.
Ultra-high strength aluminum alloy generally refers to aluminum alloy with yield strength above 500MPa, and the most common is the superhard aluminum of the 7 series. This series of aluminum alloy was originally developed in the context of aerospace applications, and has now developed into the main structural materials for military and civil aircraft in the world, accounting for 70-80% of the proportion of aircraft structural parts, and in many fields instead of expensive titanium alloys, becoming an indispensable important lightweight structural materials.
** Aerospace aluminum alloy development background and current situation **
Aluminum alloy, as a relatively mature lightweight high-strength alloy material, is used in aerospace, aluminum alloy materials are generally used as structural materials, and have higher specific strength and better processing properties than steel.
The aerospace field mainly develops high-strength, high-toughness and corrosion resistance aluminum alloy materials to meet the harsh conditions of aerospace use, the application is more 2000 series and 7000 series aluminum alloy, on the basis of high-strength aluminum alloy process improvement and material formula improvement, Through innovative production processes such as powder metallurgy and jet molding, lightweight aluminum alloy materials with better performance are developed, and related research on aluminum matrix composite materials and superplastic aluminum alloy materials is carried out.
In the development and application process of lightweight high-strength aluminum alloy, stress corrosion problem is the main problem in the entire application history of aluminum alloy, how to weaken or delay the stress corrosion problem in the use of high-strength aluminum alloy has become the main problem in the application process of aluminum alloy.
2000 series aluminum alloy is mainly Cu as the main alloying element, aluminum alloy material to add the appropriate amount of Cu element prepared in the strength, heat resistance, processing performance will be better improved, but the corrosion resistance will be reduced, because the introduction of Cu element will make it easier to show intercrystalline corrosion inside the aluminum alloy, the material composition elements directly affect the performance of aluminum alloy. Therefore, the 2000 series aluminum alloy is generally coated with pure aluminum or 6000 series aluminum alloy on the surface as an electrochemical protective film of the main aluminum alloy to improve its corrosion resistance. Later, scholars have done a lot of research on the methods to improve the stress corrosion performance of different grades of aluminum alloy, which has delayed the degree of stress corrosion of aluminum alloy to a certain extent.
In the aerospace field, the main composition of 2000 series aluminum alloy is mainly aluminum (Al), copper (Cu) and magnesium (Mg), and the main composition of 7000 series aluminum alloy is Al, zinc (Zn), Mg and Cu. There are also some high-performance (high strength, high toughness, corrosion resistance) aluminum alloy materials obtained by adding some special elements. At present, the main method to obtain high performance aluminum alloy materials is to change the melting and casting conditions.
Aluminum alloy material is an important component material to ensure the safe flight of aircraft. The selection and performance prediction of aluminum alloy materials in different parts are directly related to the safety and reliability of aircraft. The failure prediction of aluminum alloy materials in aviation is directly related to life safety and needs to be paid extensive attention.
** Foreign aerospace aluminum alloy material development **
In the 1960s, the United States improved on the basis of 7075 aluminum alloy and developed a stronger, tougher and more stress-corrosion resistant 7050 alloy, mainly used in the F-18 compression structural parts, and then developed 7150 alloy for the manufacture of Boeing 757/767 and Airbus A301 and other civil large aircraft upper wing structure. In the 1980s, the United States and other successfully developed 7055 alloy on the basis of 7150, the strength is about 10% higher than 7150, and has high comprehensive performance, which is used for the upper wing skin and wing stringer of Boeing 777 aircraft.
** The gap between China and international advanced level and the direction of development **
In China, although aluminum alloy materials have been developed for many years, there is still a big gap compared with the international advanced level. The specific performance is: first, the products are mostly imitation, the aluminum alloy material with comprehensive independent intellectual property rights is not yet available, and the standard system for the production of aluminum alloy materials has not yet been established; Second, the basic research is weak, the development time is short, and the data accumulation is insufficient; Third, the production and processing equipment is backward, and the product quality control system is not perfect.
In view of this, the future development direction of aluminum alloy materials in China should be:
Change the content and ratio of component elements;
Develop aluminum alloy material formulations corresponding to different performance requirements, improve the performance of aluminum alloy by changing the solidification field conditions, improve the solid solution amount of alloy elements, and improve the performance of aluminum alloy by adding elements such as zirconium (Zr), scandium (Sc), erbium (Er) and other microalloying methods;
Further purify the alloy, reduce Fe, Si and other impurities, control the content of impurities, and produce high-toughness and high-strength aluminum alloy materials;
Develop new heat treatment technology, establish different heat treatment process cards for aluminum alloys with different performance requirements, and establish corresponding technical standard specification system to ensure the process stability of different grades of aluminum alloys.
JIYGO REFRACTORY & ABRASIVE LIMITED
