Application of rare earth in aluminum alloy

Rare earth elements play a significant role in the metallurgical industry due to their high chemical reactivity, low potential, and unique electronic structure, allowing them to interact with almost all elements. China possesses abundant rare earth resources, characterized by diverse types, high quality, wide distribution, and ease of extraction. With proven reserves of 370 million tons, China accounts for approximately 80% of the world's total, making it the leading country in rare earth reserves. In recent years, rare earths have found extensive applications across various sectors such as metallurgy, machinery, petrochemicals, electronics, atomic energy, medicine, agriculture, aerospace, and defense. Their use in aluminum and its alloys began later than in other countries, with foreign nations starting in the 1930s and China following in the 1960s. Despite this, China has made rapid progress, particularly in enhancing the properties and performance of aluminum alloys. These improvements are mainly observed in aluminum-silicon casting alloys, aluminum-magnesium-silicon (zinc)-based deformed alloys, aluminum wires, and piston alloys. Research into the effects of rare earths on aluminum and its alloys, along with their mechanisms, has also advanced significantly. **First, the role of rare earth in aluminum and its alloys** Rare earth elements are highly reactive and can form stable compounds with gases like hydrogen, non-metals like sulfur, and metals. Their atomic radius is smaller than that of common metals like lead or magnesium, resulting in limited solid solubility and minimal formation of solid solutions. Adding rare earth elements to aluminum alloys serves as a microalloying agent. Additionally, they have a strong affinity for gases and nonmetals, forming high-melting-point compounds that help remove hydrogen, refine the alloy, and improve its structure. The high chemical activity of rare earth elements allows them to adsorb at grain boundaries, hindering crystal growth and refining the grain size. **1. Metamorphism** Metamorphism involves adding small amounts of modifiers to a metal or alloy to alter its crystallization process, improving its structure and properties. Rare earth elements act as grain refiners or inoculants. Due to their larger atomic radius compared to aluminum, they dissolve easily in molten aluminum, filling surface defects and reducing interfacial tension. This increases the nucleation rate and forms a surface active film that prevents grain growth, thereby refining the microstructure. As foreign nuclei, rare earth-aluminum compounds increase the number of crystal nuclei during solidification, significantly affecting 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 earths exhibit varying metamorphic abilities; lanthanum (La) and europium (Eu) show strong effects, while mixed rare earths and cerium (Ce) have moderate results. The metamorphic ability decreases as the atomic radius decreases from La (0.187 nm) to Er (0.175 nm). When the atomic radius is below 0.18 nm, the effect becomes negligible. Studies indicate that the critical metamorphic cooling rate (Vc) determines the effectiveness of rare earths. A lower Vc indicates a more pronounced metamorphic effect. To achieve stable metamorphic structures, it is essential to minimize rare earth loss and prevent segregation, ensuring uniform diffusion into the aluminum melt. Increasing the metamorphic temperature and strengthening post-treatment processes, such as slag removal, enhances the effectiveness of rare earths. Avoiding halogen fluxes during refining and maintaining high temperatures for an extended period ensures maximum metamorphic performance. **2. Purification** **(1) Degassing Effect of Rare Earth and Its Influence on Porosity** During the casting of aluminum alloys, a significant amount of gas, primarily hydrogen (about 85%), dissolves in the molten metal. Hydrogen is a major cause of porosity in castings, reducing mechanical strength. Adding rare earth elements can effectively remove hydrogen. When the rare earth content is less than 0.3%, the degassing effect is most pronounced, significantly reducing porosity. However, beyond 0.3%, the hydrogen content starts to rise again, with Y and La showing better results than mixed rare earths. It is recommended to keep the rare earth content below 0.3% for optimal performance. Rare earths also react with oxygen and nitrogen, forming refractory compounds like Re₂O₃ and ReN₂, which are removed as slag during smelting. At temperatures below 200°C, rare earths react with fluorine and chlorine, eliminating these impurities from the alloy. **(2) Effect of Rare Earth on Inclusions and Impurity Removal** Aluminum and its alloys contain various inclusions such as Al₂O₃, which negatively impact processability and mechanical properties. Adding 0.2% rare earth to pure aluminum modifies the microstructure, transforming coarse phases into spherical ones and reducing brittle compounds at grain boundaries. This improves plasticity and overall performance. Similarly, in aluminum alloys, rare earth addition reduces impurities like iron, purifying grain boundaries and enhancing strength and ductility. Rare earth oxides, with high melting points and densities, sink during standing, reducing residual inclusions. They also stabilize the melt, minimizing secondary oxidation and oxide formation. Rare earths outperform traditional deoxidizers like Al, Mg, and Ti in removing oxygen and sulfur, forming stable compounds that float to the surface, acting as heterogeneous nuclei during solidification. **3. Alloying** The strengthening of aluminum alloys through rare earth elements includes grain refinement, limited solid solution strengthening, and second-phase strengthening. Depending on the rare earth content, it may exist as a solid solution, segregate at phase boundaries, or form compounds. At low concentrations (<0.1%), rare earth acts as a solid solution, increasing deformation resistance and strength. At higher concentrations (>0.1%), new rare earth-containing phases form, altering the shape and distribution of second phases, further enhancing the alloy’s 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 products, including building materials, household appliances, and sporting goods. In conductive aluminum alloys, rare earths enhance electrical conductivity, making them ideal for overhead transmission lines, cables, and specialized wires. These alloys have evolved from 3.15 kV to 500 kV systems, with wire cross-sections ranging from tens to hundreds of mm². They offer high strength, large current-carrying capacity, and long service life. Rare earth-aluminum intermediate alloys are commonly used to reduce oxidative losses and simplify handling. They ensure consistent composition and reliable quality when added to aluminum. In capacitor-grade high-purity aluminum, rare earths improve corrosion resistance and capacitance, enabling smaller, more efficient capacitors. In architectural profiles like 6063 aluminum, rare earth addition enhances mechanical and processing properties, improving surface finish and durability. Rare earth aluminum alloys are also used in window screens, daily-use products, and aerospace components, offering superior strength, corrosion resistance, and cost-effectiveness. These alloys have seen widespread adoption, with notable success in manufacturing pots, pans, and household items. **6. Other Applications** Rare earths have also found success in aerospace, where heat-resistant alloys have been developed for advanced applications. In the pen-making industry, rare earth-modified aluminum has replaced high-purity aluminum, offering improved performance. Additionally, rare earth alloys are used in printing plates, automotive parts, and home appliances, demonstrating broad potential and promising future development. **Global Hardware Network** [Image: Global hardware network] **Concerned about surprises** **Label:** Rare Earth Daily Aluminum Products **Previous:** Basic knowledge of radioactivity in rare earth production **Next:** Focus on new developments in agricultural rare earth

Magnetic Valve

A magnetic valve is a type of valve that uses an electromagnetic field to control the flow of fluids or gases. It consists of a coil of wire that generates a magnetic field when an electric current flows through it. This magnetic field interacts with a ferromagnetic core, which moves a plunger or armature to open or close the valve. Magnetic valves are commonly used in industrial applications, such as in water treatment plants, chemical processing plants, and HVAC systems. They are also used in medical equipment, such as oxygen concentrators and anesthesia machines. Magnetic valves are known for their high reliability, fast response times, and low power consumption.

Magnetic Valve,Magnetic Gas Valve,Electro Magnetic Valve,Magnetic Latching Solenoid Valve

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