Use editing broadcast

Add trace of scandium in aluminum alloy, can promote grain refinement, improve the recrystallization temperature 250ºC ~ 280ºC, aluminum alloy is a powerful grain refiner and effective inhibitor of recrystallization, the structure and performance of the alloy has a significant impact, so that its strength, hardness, welding performance, corrosion resistance has been greatly improved. Scandium has a good dispersion strengthening effect on aluminum, which maintains a stable non-recrystallization structure in hot working or annealing treatment. Some of these alloys are cold rolled sheets with great deformation, and still maintain this structure even after annealing. The recrystallization inhibition effect of scandium can eliminate the recrystallization structure of the heat-affected zone of the weld, and the subcrystalline structure of the matrix can be directly transferred to the as-cast structure of the weld, so that the welded joint containing scandium aluminum alloy has high strength and corrosion resistance. The effect of scandium on the corrosion resistance of aluminum alloy is also due to the fact that scandium refines the grains and inhibits the recrystallization process. The addition of scandium can also make aluminum alloy with good superplasticity. After superplastic treatment, the elongation of aluminum alloy with about 0.5% scandium can reach 1100%. Therefore, al-scandium alloy is expected to become a new generation of aerospace, aviation, ship industry light structural materials, Russia has developed more than 10 grades of scandium aluminum alloy, mainly used in aerospace, aviation, ship welding load structural parts and alkaline corrosion medium environment aluminum alloy pipe, railway oil tank, high-speed train key structural parts, etc.

Technical highlights edited

The melting point of scandium is 1541ºC, and the melting point of aluminum is 660ºC. The melting point of the two metals is too different. Scandium must be added to the aluminum alloy in the form of intermediate alloy, which is the key raw material of scandium aluminum alloy. There are several methods to prepare intermediate alloy, such as admixture method, scandium fluoride, scandium oxide metal thermal reduction method and molten salt electrolysis method. Admixture method is to directly add scandium metal to aluminum alloy to prepare, scandium metal price is high, melting process burning loss is large, the cost of intermediate alloy is high; The thermal reduction method of scandium fluoride requires highly toxic hydrogen fluoride in the preparation of scandium fluoride. The equipment is complex and the thermal reduction temperature of metal is very high. The real yield of scandium oxide by thermal reduction method is only 80%. The device of molten salt electrolysis is complex and the conversion rate is not high. Through comparison and selection, it is more appropriate to prepare aluminum-scandium intermediate alloy by hot reduction of aluminum-magnesium by scandium chloride molten salt. [1]

Intermediate Alloys editor broadcast

The preparation of intermediate alloy is the key to the production of al-scandium alloy, and its preparation method is as follows:

Preparation of anhydrous scandium chloride molten salt (1) Sc2O3 was dissolved in hydrochloric acid in vacuum dehydration, and Sc2O3∶NaCl∶KCl∶NH4Cl was mixed proportionally. Evaporation, vacuum removal. The molten salt after vacuum dehydration was heated under the protection of argon gas to produce ScCl3·NaCl·KCl molten salt, namely anhydrous scandium chloride molten salt.

Aluminum magnesium scandium intermediate alloy industrial pure aluminum and industrial pure magnesium, a proportional heating melting. ScCl3·NaCl·KCl molten salt, and specific additives were added, melted, baked and cast to obtain Al-MG-Sc intermediate alloy. [1]

Application prospect editor broadcast

The application prospect of scandium-containing aluminum alloy in ships, aerospace industry, rocket missiles, nuclear energy and other high-tech sectors is very broad. By adding scandium, it is hoped to develop a series of new generation of high performance aluminum alloy materials such as ultra-high strength and high toughness aluminum alloy, high strength corrosion resistant aluminum alloy, high strength and neutron irradiation resistant aluminum alloy on the basis of the existing aluminum alloy. These alloys have attractive applications in the aerospace, nuclear and naval industries due to their excellent comprehensive properties, as well as in light vehicles and high-speed trains. Therefore, scandium-containing aluminum alloy has become another attractive and most competitive high-performance aluminum alloy structural materials after AlLi alloy. Our research and industrial production, which are rich in scandium resources, also have a certain basis. It is still the main exporter of scandium oxide. Carrying out research on AlSc alloy has an epoch-making significance for the development of aluminum alloy materials for our high technology and national defense construction, but also can give full play to the advantages of scandium resources and promote the development of our scandium industry and national economy.