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Chemical formula: Mg-Sc Specification: Customizable
Product application: The high strength, heat resistance, corrosion resistance and shape memory properties of scandium magnesium alloy can increase the wide application of magnesium alloy in the automobile industry, communications and electronics industry, medical and health, aerospace and other fields.
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Light magnesium scandium shape memory alloy
Author: X-MOL 2016-08-26
shape-memory alloys have a shape-memory effect; deformations that occur at low temperatures revert to their original (or nearly original) state at high temperatures. This makes it widely used in aerospace, where compression of shape memory alloy devices at low temperatures can reduce the space required for spacecraft transport, and after reaching the destination, the original shape can be restored at high temperatures to normal use. In 1969, the Apollo 11 lunar module in the United States used several meters in diameter after the moon landing antenna is made of shape memory alloy materials. In addition, shape memory alloys also have superelasticity, which on a macro level shows that they have much greater deformation resilience than normal metals. This property makes it widely used in medical equipment, building shock absorption and daily life, dental orthodontics, artificial bones, earthquake dampers, eye frames can be seen everywhere.
At present, common shape memory alloys are usually based on Ti, Ti-Ni, Cu, Fe, Ni, Co and other metals with high density, while light shape memory alloys based on Mg and Al and other light alloys have not been reported. Recently, Daisuke Ando and Yuji Sutou of Tohoku University, Japan, found that the Mg-Sc atomic ratio of about 4:1 can form shape memory alloy, and the density of the alloy is only about 2 g/cm3, much smaller than existing materials. The lightweight magnesium-scandium shape-memory alloy has great potential for applications in areas where weight control is critical, such as aerospace, according to work published in Science. (A lightweight shape-memory magnesium alloy. science, 2016, 353, 368-370, DOI: 10.1126/science.aaf6524)
X-ray diffraction (XRD) shows that the light metal alloy Mg -- 20.5 at % Sc has A different body centered cubic structure (bcc) after heat treatment and cooling (black line in FIG. 2 A), with a small amount of hexagonal dense packed phase (hcp). After cold rolling under stress, A new diffraction peak appears on the XRD pattern (red line A in FIG. 2). This stress-induced new phase generation process is similar to the martensitic transformation of β-phase Ti-base shape memory alloy. This hypothesis was confirmed by the observation of superlayered martensite in the sample by transmission electron microscopy (TEM)
As one of the rare earth elements to strengthen magnesium alloys, scandium has a lower diffusion capacity in magnesium alloys than other rare earth elements, and has a significant strengthening effect, which can significantly improve the strength, corrosion resistance, heat resistance and weldability of magnesium alloys. The high strength, heat resistance, corrosion resistance and shape memory properties of scandium magnesium alloy can increase the wide application of magnesium alloy in automobile industry, communication and electronics industry, medical and health, aerospace and other fields.
At present, the preparation of magnesium scandium alloy mainly includes admixture method, thermal reduction method and molten salt electrolysis method. Mixing method is to directly add scandium metal to the molten magnesium melt under the protective atmosphere, but the difference between the melting point of magnesium and scandium is too big, easy to cause the burning of magnesium and scandium, and the microstructure of scandium magnesium alloy is not uniform. Molten salt electrolysis method is to add scandium compounds into molten salt electrolyte, under the protection of inert gas, scandium metal precipitation in the cathode, diffusion into magnesium alloy to form scandium alloy, but the required device is complex, need to often replace electrolytic cell, scandium conversion rate is low, large energy consumption, high cost, and waste molten salt produced, causing pollution to the environment. For example, patent 201110140776.x uses water-chloride electrolysis to prepare magnesium rare earth alloy, but water-containing scandium chloride is easily hydrolyzed and converted into scocl in the preparation process, rather than into scandium chloride. In addition, the current used in this method is 1000 ~ 2000a and the temperature is 820 ~ 1100ºC, which has the disadvantages of large energy consumption, high temperature and easy burning of scandium and magnesium. Therefore, the molten salt electrolysis method is not suitable for the preparation of scandium and magnesium alloys.
Thermal reduction method is based on scandium compounds as raw materials, halide as molten salt, magnesium metal as reducing agent, scandium raw materials reduced to scandium metal at high temperature, and to the diffusion of magnesium melt, the final casting of scandium magnesium alloy, theoretically easier to operate, however, there are also some difficulties, the most prominent problem is that the molten salt system of thermal reduction reaction is not easy to control, And cause the reduction reaction is not complete, resulting in high impurity content of products affect the quality of alloy or scandium yield is low. In addition, such as the patent cn100546456 disclosed a preparation method of scandium magnesium alloy, specifically is the non-high purity scandium oxide by chlorination scandium chloride mixed molten salt, and then magnesium as reducing agent to produce intermediate alloy. However, in the preparation of mixed molten salt, the stabilizer nh4cl is required, resulting in the subsequent pollution of ammonia nitrogen wastewater. In addition, aluminum is added in the hot reduction process as a collector, resulting in aluminum in scandium magnesium alloy, thus affecting the application of scandium magnesium intermediate alloy.
Based on the above reasons, it is necessary to provide a simple operation, high product purity of scandium magnesium alloy preparation process.
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