From the early 1970s to the late 1990s, the former Soviet Union extracted and recovered scandium from metallurgical waste residue and tailings of non-ferrous metals such as tungsten, titanium, uranium, aluminum, etc., carried out a large number of basic research and application development mainly for military purposes, forming a relatively complete research, production, application and development system of scandium and its materials. After the first International Scandium Metallurgy and Scandium Materials Science and Technology Conference in Moscow in 1994, a round of scandium research and development upsurge was set off worldwide.
China is rich in scandium resources and is a major producer and exporter of primary scandium metallurgical products on the world market. However, its deep processing and application research and development are still in the primary stage. Strengthening the research, production, application and development of scandium metallurgy and scandium materials, establishing a distinctive industrial system of scandium metallurgy and scandium materials, and transforming the advantages of scandium resources into resources technology advantages are the urgent tasks for the scientific and technological development of scandium metallurgical materials in China.
Scandium is a strong modifier for aluminum alloy casting grain structure and a strong recrystallization inhibitor for semi-finished products. Adding trace scandium can greatly improve the comprehensive properties of traditional aluminum alloys. Scandium must be added in the form of master alloy in the production of industrial aluminum scandium alloy. The aluminum scandium master alloy is the key raw material for the production of industrial aluminum scandium alloy.
In order to make the master alloy melt faster when adding molten aluminum, it is required that the melting point of the master alloy should be as close as possible to the melting temperature of the aluminum alloy. The scandium content in the scandium master alloy is generally 2% - 4% (mass fraction, the same below). The intermediate alloy shall also have uniform composition and accurate test results. In order to play a better role in grain refinement of scandium master alloy, the intermetallic compound particles in the master alloy should not be too large and should be evenly distributed. In addition, the impurity content of the master alloy also has certain requirements. Practice shows that the quality of master alloy has a great influence on the properties of industrial Al Sc alloy.
The production methods of Al Sc master alloy can be divided into several categories, such as pairing method, molten salt electrolysis method, vacuum and non vacuum aluminothermic reduction method. The researchers are mainly concentrated in Russia, the United States and China, which may be related to the early start of aluminum scandium alloy research in these countries, and they are all countries with large scandium resources.
