Magnesium-rare earth alloys are a type of lightweight structural material with low density and high performance. They have broad application prospects in the aerospace, defense, military, and automotive industries. In recent years, significant progress has been made by researchers in the preparation, processing techniques, and application studies of magnesium-rare earth alloys.
However, challenges and technological bottlenecks still exist in material composition design, melt purification and refinement, material preparation and forming techniques, as well as industrial application.
Development of high-performance magnesium-rare earth alloy material systems
Rare earth elements (RE) are typically divided into two categories: light rare earths and heavy rare earths. High-strength and heat-resistant Mg-RE alloys are mainly based on heavy rare earths, such as Mg-Gd, Mg-Y, Mg-Nd, Mg-Dy, Mg-Sm, etc. Magnesium-rare earth alloys have the advantage of high strength combined with low density. The yield strength and tensile strength of common cast aluminum alloys and magnesium alloys concerning the density of light metals are shown in Figure 1. Mg-Gd and Mg-Y alloys have strong age-hardening ability and potential for practical processing, which makes them the most studied alloys and the basis for existing high-performance magnesium-rare earth alloys.
Research on the castability, melt purification, and grain refinement of magnesium-rare earth alloys
During the smelting and casting processes of magnesium alloys, factors like castability, melt purity, and grain size control are crucial. Magnesium-rare earth alloys demonstrate good castability and can meet various application requirements. Researchers have conducted experimental studies on both metal mold and sand mold casting. Rare earth elements, as the main alloying elements, affect the melt's activity, necessitating melt purification. Special fluxes and composite purification methods suitable for magnesium-rare earth alloys have been developed. In terms of grain refinement, researchers have explored methods like substituting Mg-Zr intermediate alloys and adding pure aluminum to in-situ form Al2RE-type intermetallic compounds, achieving refined grain sizes in magnesium-rare earth alloys.
Liquid forming processes for magnesium-rare earth alloys
Magnesium-rare earth alloys can be processed using various liquid precision forming techniques, such as low-pressure sand casting, vacuum high-pressure die casting, squeeze casting, and semi-solid forming. These processes improve production efficiency and enhance component performance. Low-pressure sand casting is suitable for large, thin-walled, and complex-shaped parts. Vacuum high-pressure die casting produces strengthened magnesium alloys. Squeeze casting achieves dense components, which can be further strengthened through heat treatment. Semi-solid forming techniques, like thixotropic forming and reforming, produce parts with improved mechanical properties. However, challenges remain in preparing semi-solid slurry and implementing reforming for magnesium-rare earth alloys, requiring further research.
Industrial applications of magnesium-rare earth alloys
Magnesium-rare earth alloys have various applications in the aerospace, defense, and automotive industries. In aerospace, these alloys are used in components like commercial aircraft seats, taking advantage of their strength and flame retardancy. However, in the civilian sector, their application is limited due to cost factors. Nevertheless, with the optimization of materials and process costs, it is anticipated that magnesium-rare earth alloys will find more industrial applications in the civilian sector.
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