Recently, BTXT Rare Earth Research Institute has developed a rare earth magnesium-zirconium grain refiner product with a zirconium particle size below 600 nm, which fills the gap in the product of high-efficiency and low-cost magnesium alloy grain refiner.
"This provides the possibility of developing high-strength cast / deformed magnesium alloy materials for rail transportation equipment such as aircraft seats, automobile safety components, and high-speed train lightweighting." Said Hu Wenxin, senior engineer and director of the magnesium alloy project team of the Rare Earth Research Institute.
New breakthrough in grain refiner technology
At present, China's industrial field generally uses magnesium-zirconium intermediate alloys as grain refiners. Existing products in the market have low refining efficiency of zirconium elements (less than 40%), large deposits of zirconium particles, high cost of refiners, and high impurity content. As well as the instability of refinement process operation and many other problems, it brings great difficulties to practical industrial applications.
"The grain size control technology of magnesium alloys is one of the most fundamental and most significant technical methods for regulating the performance of magnesium alloy materials. Zirconium and rare earth elements are effective refinement elements of magnesium alloys. How to make full use of these elements in The role of alloys is the focus of our research. "Hu Wenxin said.
Based on the previous research results on the coupling and refinement mechanism of rare earth and zirconium elements on magnesium alloys, BTXT Rare Earth Research Institute is supplemented by a new metallurgical process preparation method to allow more densely distributed and smaller volume zirconium particles to provide more magnesium crystal core At the same time, the rare earth element enhances the adhesion ability of the magnesium nucleus on the surface of the zirconium particles during the crystallization process, and can achieve high-efficiency refinement of the magnesium alloy grains.
The data shows that the particle size after refining is 30% of the size of the zirconium particles in the traditional magnesium-zirconium master alloy, the nano-scale particle size distribution rate is greater than 60%, the agglomeration between particles is less than 5%, and the alloy grains in the as-cast state The size is reduced by 20% to 35 mm or less, and the grain refinement effect is remarkable.
At present, the product has completed the research and development of small-scale production technology, and the product has been verified by the customer. The product refining efficiency is greater than 80%, and the cost is more than 20% lower than the traditional magnesium-zirconium grain refiner.
Hu Wenxin said: "This technology is of great significance to the industrialization of rare earth magnesium alloy ingot products. It can effectively reduce the unevenness of the internal and external metal particles of the product, keep the internal and external alloy particle size basically consistent, and greatly increase the stress level of the alloy. To make the alloy more durable. "
Rare earth magnesium alloy product application has been newly improved
With the rapid development of new energy vehicles and domestic 5G communications, there is a strong market demand for lighter alloy materials that are lighter, have better heat dissipation, and have excellent corrosion resistance, but the corresponding performance requirements are becoming more demanding.
"We studied the mechanism of lanthanum, cerium and other rare earth elements on the heat dissipation performance of magnesium alloys, and developed low-cost heat dissipation rare earth magnesium alloy engineering materials with a thermal conductivity of 100 W / (m × K). The comprehensive evaluation performance has been equivalent to existing aluminum alloys. The heat dissipation material saves more than 5% cost than using aluminum alloy. "Hu Wenxin said confidently.
Based on the mechanism of action of rare earth on the heat dissipation performance of magnesium alloys and the breakthrough in the technology of controlling the grain size of magnesium alloys, BTXT Rare Earth Research Institute has made new breakthroughs in the industrialization of semi-continuous casting and cold chamber die casting.
At present, there are few special studies on the die casting process of rare earth magnesium alloys at home and abroad. "We, jointly with Northeastern University and Shanghai Jiaotong University, have independently developed semi-continuous casting technology, breaking through melt purification fine crystal technology, low-frequency electromagnetic casting control technology, self-flow casting control technology and other technologies. Magnesium alloy rods have large internal stresses, large radial grain size differences, and uneven mechanical properties. "Hu Wenxin said that this synthesis technology represents the domestic leading magnesium alloy material semi-continuous casting technology, which is the subsequent large size and high The low cost of high-quality forged wheels and extruded profiles lays the foundation for technology and products.
Not only that, the QC830 cold chamber die casting system introduced by the BTXT Rare Earth Research Institute has a system clamping force of 850t, a maximum injection force of 756 kN, and a maximum projected area of 1242 cm2. At present, it has a large size rare earth to achieve a maximum diameter of 550 mm The industrial preparation technology of magnesium alloy rods, while relying on the pilot platform, realizes the pilot-scale preparation of large-sized rod products, realizes the production capacity of 300 tons / year of rare earth magnesium alloy thin-walled devices, and accelerates the promotion of rare earth magnesium alloy materials Downstream terminal applications.
For future technology research and development, Hu Wenxin said that the research and development team will target high-performance heat-dissipating magnesium alloys and functional magnesium alloy materials for the communications engineering and civil electronics industries; Realize the demonstration application of corresponding devices and products.