A High Performance Aluminum Alloy: Al-Sc Alloy

Al-Sc alloy is a kind of high-performance aluminum alloy. There are several ways to improve the performance of aluminum alloy, among which micro-alloying strengthening and toughening is the frontier field of high-performance aluminum alloy research in recent 20 years.

The melting point of scandium is 1541℃, and that of aluminum is 660℃, so scandium must be added to aluminum alloy in the form of master alloy, which is the key raw material for preparing aluminum alloy containing scandium. There are several methods to prepare master alloys, such as doping method, scandium fluoride, scandium oxide metal thermal reduction method, molten salt electrolysis method and so on. “

The doping method is to directly add metal scandium to aluminum alloy, which is expensive, burning loss in smelting process and high cost of master alloy

Toxic hydrogen fluoride is used in the preparation of scandium fluoride by metal thermal reduction method of scandium fluoride, which has complex equipment and high metal thermal reduction temperature

The recovery rate of scandium by metal thermal reduction of scandium oxide is only 80%;

The molten salt electrolysis device is complex and the conversion rate is not high.

After comparison and selection, it is more appropriate to prepare Al-Sc master alloy by using ScCl molten salt Al-Mg thermal reduction method.

Uses:

Adding trace scandium to aluminum alloy can promote grain refinement and increase recrystallization temperature by 250℃~280℃. It is a powerful grain refiner and an effective recrystallization inhibitor for aluminum alloy, which has obvious influence on the structure and properties of the alloy and greatly improves its strength, hardness, weldability and corrosion resistance.

Scandium has a good dispersion strengthening effect on aluminum, and maintains a stable non-recrystallized structure in hot working or annealing treatment. Some alloys are cold rolled sheets with great deformation, which still maintain this structure even after annealing. The inhibition of scandium on recrystallization can eliminate the recrystallization structure in the heat affected zone of weld,The subgrain structure of the matrix can be directly transferred to the as-cast structure of the weld, which makes the welded joint of aluminum alloy containing scandium have high strength and corrosion resistance.

The effect of scandium on the corrosion resistance of aluminum alloy is also due to the grain refinement and inhibition of recrystallization process.

The addition of scandium can also make the aluminum alloy have good superplasticity, and the elongation of aluminum alloy with 0.5% scandium can reach 1100% after superplastic treatment.

Therefore, Al-Sc alloy is expected to become a new generation of lightweight structural materials for aerospace, aviation and ship industries, which are mainly used for welding load structural parts of aerospace, aviation and ship, aluminum alloy pipes for alkaline corrosive medium environment, railway oil tanks, key structural parts of high-speed trains, etc

Application prospect:

Sc-containing aluminum alloy has a wide application prospect in high-tech departments such as ship, aerospace industry, rocket and missile, nuclear energy, etc. By adding trace scandium, it is hopeful to develop a series of new-generation high-performance aluminum alloy materials based on the existing aluminum alloy, such as ultra-high strength and high toughness aluminum alloy, high-strength corrosion-resistant aluminum alloy, high-strength neutron irradiation resistant aluminum alloy and so on.These alloys will have a very attractive application prospect in aerospace, nuclear energy and shipbuilding industries because of their excellent comprehensive properties, and can also be used in light vehicles and high-speed trains. Therefore, scandium-containing aluminum alloy has become another attractive and most competitive high-performance aluminum alloy structural material after AlLi alloy.China is rich in scandium resources and has a certain foundation for scandium research and industrial production, which is still the main exporter of scandium oxide. It is of epoch-making significance to develop aluminum alloy materials for high-tech and national defense construction in China, and it can AlSc give full play to the advantages of scandium resources in China and promote the development of scandium industry and national economy in China.