Application of rare earth in aluminum alloy

Rare earth elements play a crucial role in the metallurgical industry due to their unique properties. These metals are highly reactive, possess low potential, and have a special electronic configuration, allowing them to interact with almost all other elements. China is one of the richest countries in terms of rare earth resources, boasting a wide variety of elements, high quality, broad distribution, and ease of extraction. With proven reserves of approximately 370 million tons, China holds about 80% of the world's total, making it the leading country in this field. In recent years, rare earths have found extensive applications across various industries, including metallurgy, machinery, petrochemicals, electronics, nuclear energy, medicine, agriculture, aerospace, and defense. The use of rare earths in aluminum and its alloys began later compared to foreign countries—starting in the 1960s in China—but has since developed rapidly, especially in improving the performance and application of these materials. Their effects are most noticeable in aluminum-silicon casting alloys, aluminum-magnesium-silicon (zinc)-based deformed alloys, aluminum alloy wires, and piston alloys. Research into the influence of rare earths on aluminum alloys and their mechanisms of action has also made significant progress. **First, the role of rare earth in aluminum and its alloys** Rare earth elements are highly reactive and can easily form stable compounds with gases like hydrogen, non-metals such as sulfur, and other metals. Due to their smaller atomic radius compared to common metals like lead or magnesium, they have very low solubility in these materials and rarely form solid solutions. When added to aluminum alloys, rare earths act as microalloying agents. Additionally, they have a strong affinity for gases and non-metals, forming high-melting-point compounds that help remove hydrogen, refine the structure, and improve the alloy’s properties. Their high chemical activity also allows them to adsorb at grain boundaries, hindering crystal growth and resulting in grain refinement. **1. Modification** Modification refers to the process of adding small amounts of modifiers to metals and alloys to alter their crystallization behavior, thereby enhancing their microstructure and mechanical properties. Rare earth elements, which are more active than aluminum, dissolve easily into molten aluminum, filling surface defects and reducing interfacial tension between new and old phases. This promotes faster nucleation and the formation of a surface-active film that prevents grain growth, refining the microstructure. As foreign nuclei, rare earth-aluminum compounds increase the number of crystal nuclei during solidification, significantly influencing the alloy’s structure. Rare earths are particularly effective in modifying aluminum-silicon alloys, transforming needle-like and flake eutectic silicon into spherulites and reducing primary silicon. Different rare earth elements exhibit varying modification abilities, with lanthanum (La) and europium (Eu) being the most effective. Mixed rare earths and cerium (Ce) show moderate results. The modification ability decreases as the atomic radius decreases, becoming negligible when it falls below 0.18 nm. Studies indicate that the critical modification cooling rate (Vc) determines the effectiveness of rare earths. A lower Vc means a more pronounced modification effect. **2. Purification** **(1) Degassing Effect of Rare Earth and Its Influence on Porosity** During the casting of aluminum and its alloys, a large amount of gas, mainly hydrogen (about 85%), is dissolved in the melt. Hydrogen is the main cause of porosity, significantly reducing the strength of the castings. Adding rare earths can effectively reduce hydrogen content. At concentrations below 0.3%, the degassing effect is most pronounced, with the largest reduction in porosity. Beyond 0.3%, the hydrogen content begins to rise again. Yttrium (Y) and La show the best dehydrogenation effects, followed by mixed rare earths. Proper control of rare earth addition is essential for achieving stable microstructures. **(2) Removal of Impurities and Impact on Inclusions** Impurities such as Al₂O₃ and other non-metallic inclusions negatively affect the processability and mechanical properties of aluminum alloys. Adding rare earths can transform these inclusions into spherical structures, reducing their harmful effects. For instance, adding 0.2% rare earth to pure aluminum modifies the original coarse phase, forming spherical rare earth phases and eliminating brittle fragments. This improves the plasticity and overall performance of the alloy. Rare earths also help purify grain boundaries by redistributing impurities and reducing the presence of high-iron phases. There are two key reasons why rare earths significantly reduce inclusions: 1. Rare earth oxides have high melting points and specific gravity, causing them to sink during the standing process, thus reducing residual inclusions. 2. Rare earths stabilize the melt, minimizing secondary oxidation and the formation of new oxide films. Their deoxidizing and desulfurizing capabilities further enhance the purity of the alloy. **3. Alloying** The strengthening effect of rare earths in aluminum alloys includes grain refinement, limited solid solution strengthening, and second-phase strengthening from rare earth compounds. At low concentrations (<0.1%), rare earths exist primarily in the matrix and at grain boundaries, contributing to deformation resistance and dislocation promotion. At higher concentrations (>0.1%), they form new phases that refine the microstructure, improving mechanical properties. **Second, the Application of Rare Earth in Aluminum and Its Alloys** Various rare earth-containing alloys have been developed for their unique physical and chemical properties. Rare earths are widely used in military, agricultural, industrial, and consumer sectors, including construction, household appliances, and sports equipment. In conductive aluminum alloys, rare earths have shown great potential, particularly in high-voltage transmission lines and specialized wires. They offer improved strength, current-carrying capacity, and durability. Over 20 provinces in China produce rare earth aluminum wire, with annual output exceeding 100,000 tons. **1. Rare Earth-Aluminum Intermediate Alloys** Due to the high reactivity and difficulty in handling single rare earth metals, intermediate alloys are commonly used. These reduce oxidation loss, simplify handling, and ensure stable composition and quality. **2. Application in High-Purity Aluminum Foils** Adding trace rare earths to high-purity aluminum enhances the corrosion coefficient and performance of capacitors, leading to smaller, more efficient devices. **3. Use in Aluminum Building Profiles** In 6063 aluminum profiles, rare earth additions improve mechanical and processing properties, increase hardness, and enhance surface finish and corrosion resistance. **4. Application in Aluminum Alloy Window Screens** Rare earth alloys improve strength, corrosion resistance, and cost-effectiveness, making them popular in both domestic and international markets. **5. Daily Aluminum Products** Rare earths enhance the mechanical properties, deep-drawability, and corrosion resistance of daily-use aluminum products, such as pots, cups, and plates. These products meet national standards and are widely used. **6. Other Applications** Rare earths have also been successfully applied in aerospace, printing, and other specialized fields, demonstrating their versatility and value. In summary, rare earths play a vital role in enhancing the properties and applications of aluminum and its alloys, contributing to advancements in multiple industries.

Check Valve

The check valve is used in the piping system, its main function is to prevent the backflow of the medium, prevent the pump and its driving motor from reversing, as well as the release of the medium in the container.


Check valves can also be used to feed pipes where the pressure may rise to exceed the pressure of the main system. Check valve according to the different material, can be applied to a variety of media pipeline.


The check valve is installed on the pipeline, which becomes one of the fluid components of the complete pipeline. The opening and closing process of the valve disc is affected by the transient flow state of the system in which it is located. In turn, the closing characteristics of the disc have an effect on the fluid flow state.

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