Aluminum is the most abundant metal element in the earth’s crust. It is the nonferrous metal with the second largest output and usage in the world after steel. It has a low density, about 1/3 of steel. Since pure aluminum is soft and has low strength, therefore, by adding a small amount of elements such as magnesium, copper, zinc, silicon, and lithium to aluminum, the performance of aluminum alloy is better. Aluminum alloys are the most widely used nonferrous metal structural materials in industry because of their excellent mechanical properties and corrosion resistance. They have been widely used in construction, aerospace, automobile, machinery manufacturing, shipbuilding and chemical industries.
Aluminum alloys have excellent properties in mechanics and chemistry:
① Mechanical aspects, mainly reflected in low density, high strength, high modulus, etc. Aluminum has a low density and is lighter than other metals, only 1/4 of steel, so it is suitable for use in fields with high requirements for lightweight ;
② In terms of chemical properties, since aluminum alloy can form a dense oxide film on its surface in the air, it can protect itself from deep oxidation. Therefore, it has excellent corrosion resistance and a very stable chemical composition.
③Aluminum alloy has good plasticity and can be processed into various profiles. It has excellent electrical and thermal conductivity. Therefore, it is widely used in industry, and its usage is second only to steel.
At present, there are more than 250 aluminum alloys with different compositions in the industry. In order to facilitate the distinction, according to the different alloy compositions, China adopts the internationally accepted four-digit grade classification method to facilitate the production site marking, memory and calculation management. The aluminum alloys used in the military industry mainly include aluminum-lithium alloys, 2XXX (A1-Cu-Mg) series and 7XXX series aluminum alloys.
Market demand and development trend of various aluminum alloy materials
2XXX series aluminum alloy
2XXX (A1-Cu-Mg) series aluminum alloys have high tensile strength, toughness and fatigue strength, good heat resistance, processing and welding properties, and are widely used in aerospace , automotive and weapons industries. The main grades are 2A01, 2A02, 2A06, 2A11, 2A12, etc. A series of alloys have been developed to improve strength, toughness matching, and damage tolerance, such as 2024, 2124, 2524, 2324 alloys, etc.
China’s equipment models are developing in the direction of lightweight, long life, high reliability and low cost, and have high requirements for the fracture toughness, crack propagation resistance and corrosion resistance of the fuselage skin material. Based on the 2024-T351 aluminum alloy thick plate, foreign countries have developed 2324, 2624 and other high damage tolerance aluminum alloys for the lower wing surface with different strength, toughness, fatigue and corrosion resistance, and have achieved installation and application. China is developing high damage tolerance 2XXX series aluminum alloys. In the future, composite microalloying will be an important development direction for Al-Cu-Mg series high-strength aluminum alloys.
4XXX series aluminum alloy
At present, eutectic and hypoeutectic Al-Si alloys are mainly used for automobile pistons in China. However, with the continuous improvement of engine performance requirements, it is difficult to meet performance requirements. Hypereutectic Al-Si alloy has low density, small linear expansion coefficient, higher wear resistance and volume stability, and is a more ideal piston material compared with eutectic Al-Si alloys. Hypereutectic Al-Si alloy pistons have been mass-produced abroad and applied to trucks and cars, such as A390 alloy in the United States, AC9A and AC8A (ZL109) alloys in Japan, and A390 alloy in Australia. However, there are currently few manufacturers in China that produce hypereutectic Al-Si alloy pistons, and most of them rely on imports. In addition, there is a large gap between automotive turbocharger aluminum alloy materials and foreign countries. High-performance automotive turbocharger aluminum alloy materials mainly rely on Japan and other countries. Therefore, it is imperative to develop key automotive aluminum alloy materials for high-performance pistons and turbocharger impellers.
5XXX Series Aluminum Alloys
Al-Mg alloys, especially Al-Mg alloys with high Mg content, have high specific strength, good weldability and corrosion resistance, and will become highly competitive materials in the future aerospace, high-speed trains, oceans and other fields. At present, Al-Mg alloy plates, profiles and welding wires for aerospace, trains, oceans and other applications mainly rely on imports. The high-end welding wire market is basically monopolized by ALCOA in the United States. ER5183 and ER5356 alloys mainly rely on imports, and the import volume accounts for about 70% of their sales. Al-Mg alloys for ships mainly rely on Russia. Conventional ingots of alloys with high Mg content have well-developed dendrites, severe eutectic phase segregation, and poor forming performance. The current processing methods still have many problems, such as low performance, poor apparent quality, long process, unstable quality, and low yield. Sub-rapid solidification and forming can inhibit the precipitation of Mg, and at the same time can be regulated to obtain fine equiaxed crystals and nano-precipitated phases, greatly improving the performance and uniformity of the material. Therefore, the development of sub-rapid solidification continuous rheological extrusion and rolling technology for high-performance Al-Mg alloys is expected to meet the demand for high-quality Al-Mg alloys.
6XXX Series Aluminum Alloys
6XXX series aluminum alloy materials are key materials in the fields of rail transit, automobiles, electronics, etc. Since the 1980s, developed countries and regions such as Europe, the United States, and Japan have developed aluminum alloys for automobiles, registered grades such as 6009, 6016, 6010, 6111, 6022, and 6082, and formed a relatively complete production and application system for automobile body panels, extrusions, forgings, etc. The industrialization research and development of 6XXX series aluminum alloy body panels and forgings in China has just started, and there is a clear gap. The Ministry of Industry and Information Technology of China has proposed that the automotive aluminum alloy sheets to be developed are: 6016-S, 6016-IH, 6016-IBR, 6A16-S, 6A16-IBR, 6022, etc. The typical 6XXX series aluminum alloy sheet has an elongation A50 of not less than 25%, an r value of not less than 0.60, a 60 d parking yield strength Rp0.2 of not less than 140 N/mm2 and a paint hardening yield strength increment of not less than 80 N/mm2 . In response to different needs, the development of design, preparation and processing technology of 6XXX series aluminum alloys has become an inevitable trend of development.
7XXX Series Aluminum Alloys
7XXX series aluminum alloys have good stress corrosion resistance and are the strongest series among aluminum alloys. They are internationally recognized as aviation backbone materials. Recently, foreign countries have developed 7055 alloy (Al8Zn-2.05Mg-2.3Cu-0.16Zr), whose yield stress exceeds 620 MPa in the T77511 state. It is used in Boeing 777 aircraft and reduces weight by 635 kg. At present, China lacks systematic alloy design and preparation and processing technology for 7XXX series aluminum alloys for aviation, and some products are completely dependent on imports. Due to the large-scale ingots of 7XXX series aluminum alloys with many alloy elements, wide solidification range, large casting stress, and easy oxidation/segregation of alloy elements, the metallurgical quality of the ingots is poor and the room temperature forming performance is low, it is of great significance to develop new 7XXX series aluminum alloys.
Aluminum-lithium (Al-Li) alloy
Aluminum-lithium alloy is the fastest-growing lightweight material in aviation materials in recent years. It has the characteristics of low density, high elastic modulus, high specific stiffness, good fatigue performance, and corrosion resistance. After replacing conventional aluminum alloys, the mass can be reduced by 10%~20% and the stiffness can be increased by 15%~20%. In the early 21st century, the American ALCOA company launched the “ALCOA Aviation 20/20 Plan”, with the goal of reducing the cost and weight of aviation aluminum alloys by 20% each within 20 years. Constellium has developed 2050 and 2198 aluminum-lithium alloys (Al-Cu-Li-Mg-Ag) with low density, high toughness and high damage tolerance. There are very few Al-Li alloy grades independently developed in China, and only the 1420 alloy has been used. The aluminum-lithium alloy used in the C919 passenger aircraft is provided by Alcoa. Domestically, only limited alloy grades such as 1420, 2195, 2197, and 2A97 can be produced, and the ingots are only flat ingots below ((310~400)×1280×4000) mm and round ingots below φ650 mm. Flat ingots (2B16) with a thickness of more than 60 mm and a width of more than 1500 mm, and ingots (2B16) with a diameter of more than 1500 mm in the field of high-end aviation applications have not yet been industrially produced. Therefore, it is of great significance to develop new aluminum-lithium alloy design, ultra-large ingot preparation and deep processing technology.
Heat-resistant aluminum alloy
Heat-resistant aluminum alloys are key basic materials in the fields of aerospace, automobiles, rail transportation, etc. by regulating elements such as Si, Fe, Ni, Ag, and rare earths to make aluminum alloys resistant to oxidation and creep at high temperatures. Traditional heat-resistant aluminum alloys include: 2519, 2618, 2219, 2D70, etc. With the rapid development of the aerospace and automobile industries, higher requirements are placed on heat-resistant aluminum alloys. The new generation of fighter jets has a high cruising speed, and the operating temperature of the fuselage skin is above 150°C. At present, the long-term use temperature of heat-resistant aluminum alloys such as 2618 and 2D70 is below 150°C. It is imperative to develop new heat-resistant aluminum alloys.
Al-Sc alloy with ultra-low scandium (Sc) content
Al-Sc alloy has excellent properties such as high strength, good plasticity and corrosion resistance, and has become a new generation of lightweight materials for aerospace, ships, etc. after Al-Li alloy. The tensile strength of Al-Mg alloy containing trace amounts of scandium is 30% higher than that of 5083 alloy, and the yield strength is more than doubled. Its weldability is comparable to that of conventional 5XXX series alloys, the mechanical properties of the heat-affected zone and weld are approximately equal to those of the matrix, and its corrosion resistance is comparable to that of 5083 alloy. Replacing 5XXX or 6XXX series alloys in the manufacture of aerospace components can achieve significant weight reduction effects, and it is also a superior material for automobiles and rail vehicles. Russia is at the forefront of the world in the development of scandium-containing aluminum alloys, and has formed Al-Mg-Sc, Al-Mg-Li-Sc, Al-Zn- MgSc , Al-Zn-Mg-Cu-Sc, and Al-Cu-Mg-Sc alloys with a scandium content of 0.18%~0.5%. In order to promote the application of aluminum-scandium alloys in aerospace and automobiles, China’s Ministry of Industry and Information Technology has listed scandium -containing aluminum alloys as one of the new materials for priority development. China is rich in scandium resources and has built a high-purity scandium oxide extraction production line, laying the foundation for the development of aluminum-scandium alloys.
500 MPa grade hot stamping aluminum alloy for automobiles
There is still a blank in hot stamping high-strength aluminum alloy materials in China. The combination of new materials and new forming process development is an effective means to solve the problem of high-strength aluminum alloy automobile parts forming. Focusing on 7XXX series alloys, actively exploring 2XXX alloys, and developing 500 MPa grade aluminum alloy materials for hot stamping have important prospects for manufacturing complex-shaped automotive parts.
Aluminum-based composite materials
Aluminum-steel multilayer composite plate: The effective connection between aluminum and steel decks has become one of the constraints for lightweighting of superstructures of large ships. The aluminum-steel composite transition joint used for welding between aluminum and steel hulls provides a solution to replace the traditional riveting process. Honda has developed a steel and aluminum joining technology that will be used globally in mass-produced car frames. At present, the aluminum-steel composite joints used in China are mainly imported from abroad, with a price as high as 4×10 5 CNY/t. With the future large-scale ships, higher welding temperatures, greater bearing stress, and stronger bonding interfaces are required for transition joints, and high-performance aluminum-steel joints are urgently needed.
Post time: Mar-08-2025
