From the earliest primitive human tools to the first flight attempts, we've been looking for materials that are light and strong. Especially in the design of automotive, flying and other products, considering the requirements of safety and reliability, metal materials are undoubtedly the first choice, but the weight of steel undoubtedly distresses designers, so is there a metal that can What is the demand for lightweight design? Magnesium (alloy) is the best choice.
Magnesium (Mg) is the eighth richest element in the earth's crust, 33% lighter than aluminum, 60% lighter than titanium, and 75% lighter than steel. Magnesium alloys composed of other elements also have the outstanding advantages of low density, high specific strength, large elastic modulus, good thermal conductivity and shock absorption, strong electromagnetic shielding performance, good biocompatibility, and easy recycling. "21st Century Green Structural Materials" has also been advertised as one of the star materials in the future metal industry by many industry experts.
In today's severe situation where the world ’s energy and environmental problems are becoming increasingly prominent, magnesium alloys are increasingly used in the automotive industry, communications electronics industry, and aerospace industry. China is one of the countries with the most abundant magnesium ore resources in the world. The output of available magnesium ore resources accounts for about 70% of the world's total reserves, so it has a significant resource advantage in developing the magnesium material industry.
The density of pure magnesium is 1.738 g / cm3, and the density of magnesium alloy is only 1.75 to 1.90 g / cm3, which is about 2/3 of aluminum alloy and 1/4 of steel. The specific strength of magnesium alloy is significantly higher than that of aluminum alloy and steel, and the specific stiffness is comparable to that of aluminum alloy, which is much higher than that of engineering plastics. In the context of the rapid development of the current automotive industry, especially the new energy vehicle industry, the use of magnesium alloys as structural components can significantly reduce the weight of automobiles, effectively reduce fuel consumption, improve fuel economy, and reduce pollution emissions. The most potential applications of magnesium alloys in automobiles are overall structural components, such as steering wheels, hoods, trunk lids, roof panels, body reinforcement plates, inner door frames and rear compartment partitions, and some high-strength heat-resistant magnesium Alloys can even be used in engine cylinder blocks and automotive wheels.
Compared with aluminum alloy, steel, and iron, magnesium alloys have lower elastic modulus. Under the same stress conditions, they can consume more deformation work, have noise reduction and vibration reduction functions, and can withstand larger impact vibrations. load. These characteristics of the magnesium alloy can meet the requirements of light materials for noise absorption, shock absorption and radiation protection in high-tech fields such as aerospace, thereby improving the aerodynamic performance of the aircraft and significantly reducing the structural weight. Beginning in the 1940s, magnesium alloys were first used in the aerospace sector. Pay attention to materials science and engineering public account to learn more. In foreign countries, each of the B-36 heavy bombers used 4086kg magnesium alloy plates; the starter rocket "Hercules" of the "Drelais" spacecraft used 600kg of deformed magnesium alloy; the "Discovillaire" satellite 675kg of deformed magnesium alloy was used in the test; the "Verger" rocket shell with a diameter of about 1 meter was also made of magnesium alloy extruded tubes. Magnesium alloy components are also used on fighters, bombers, helicopters, transport aircraft, civilian aircraft, airborne radar, surface-to-air missiles, carrier rockets, satellites, and spacecraft made in China.
Magnesium alloy has good thermal and electrical properties. Although the thermal conductivity of magnesium alloy is not as good as that of aluminum alloy, it is much higher than plastics and resins. At the same time, magnesium alloy has good electromagnetic shielding performance. cover. Some well-known electronic communication brand companies have successfully used magnesium alloys in the manufacture of electronic product housings such as personal laptops, mobile phones, and video recording equipment. Of the 30 million notebook computers shipped worldwide in 2003, the proportion of aluminum and plastic casings reached 75%, and the proportion of magnesium alloys was only 25%. However, in 2004, the proportion of notebook computers using magnesium alloy casings increased to above 50.
Although magnesium alloy has many attractive performance advantages, it is still difficult to be widely used due to its inherent performance disadvantages and current technical constraints. The leader of the material industry, Academician Shi Changxu once pointed out that there are three major bottlenecks in the development of magnesium alloys, that is, the lack of effective precipitation phases, easy corrosion and difficult deformation. These three issues are also the main obstacles to the development of new high-performance magnesium alloys.
The electrode potential of magnesium is low and its chemical properties are lively, which makes magnesium alloy products easy to corrode. Therefore, the problem of corrosion is also a key factor hindering the application of magnesium alloys. There are two main technical methods to improve the corrosion resistance of magnesium alloys. One is to increase the electrode potential of the magnesium alloy substrate itself through alloying and purification treatment, or to form a self-healing protective film on the surface to enhance its own environmental corrosion. Resistance; the other is to prevent surface corrosion by forming a surface protective film through surface protection treatment. Because the former is limited by the chemical properties of magnesium and has not achieved breakthroughs in application, at present, more and more domestic and foreign researchers are committed to the research and development of surface protection technology. The foundation of micro-arc oxidation surface treatment technology that is widely used at present has opened up some new Surface treatment technology and achieved good results.
Vigorously developing the application of magnesium alloys must be based on accelerating basic research on magnesium alloys. Strengthen the basic theoretical research on the strengthening and toughening mechanism and plastic deformation mechanism of magnesium alloys, and fundamentally understand the strengthening and plastic deformation mechanisms of magnesium alloys. At the same time, the research on corrosion mechanism and failure mechanism of magnesium alloys must be strengthened. On this basis, create stress-strain conditions that are conducive to the deformation of magnesium alloys, develop new high-performance magnesium alloy systems, and produce advanced magnesium alloys with high strength, heat resistance, corrosion resistance, and good deformation properties through advanced deformed magnesium alloy processing technology.