[China Aluminum Industry Network] 1. Influence of rare earth element species The effect of single rare earth and mixed rare earth on the metamorphism of eutectic Al-Si alloys was investigated. It was found that Eu has a strong metamorphic ability, followed by La, Ce, Pr, and Nd. The metamorphic ability of the mixed rare earth is slightly lower than that of La. The metamorphic ability of rare earth decreases rapidly with the decrease of atomic radius, and Er and Y have almost no metamorphic ability, and the metamorphism of RE is sensitive to cold speed, and is suitable for metal-type castings. Stainless Steel Barbecue Grill Grate Barbecue wire Grill Grate is made of high quality 304 stainless steel, never rusting and durable. BBQ Wire mesh does not have any coating or chemical ingredients, making food safer. stainless steel wire grill grate,stainless steel BBQ grate, BBQ grill grate,BBQ grill grate custom Shenzhen Lanejoy Technology Co.,LTD , https://www.szlanejoy.com
2. Effect of rare earth element addition amount The role of rare earth in aluminum alloy is not only related to the type of rare earth element and the type of aluminum alloy, but the role of rare earth is different, and its role is also different. The addition of rare earths in ZA1Si7Mg1A alloys has increased the tensile strength and elongation of the alloys to different extents, and both of the best results have appeared when adding 4.5% RE. When the addition amount is less than this value, the tensile strength and elongation of the alloy increase synchronously with the increase of the amount of rare earth incorporation. After the addition amount exceeds 4.5%, the tensile strength and elongation of the alloy decrease simultaneously. It is pointed out that adding appropriate amounts of rare earths in Ti-B-Sr alloys with AA refinement and refinement not only has a comprehensive effect of refinement and metamorphism, but also can effectively reduce the "recession" of modifiers; at the same time, it can strengthen Sr on silicon. The metamorphic effect of the phase reduces the number of alloy pinholes and improves the metallurgical quality of the alloy. However, addition of excess rare earth may form RE-Sr intermetallic compounds, weakening the effect of Sr on the modification of the silicon phase; the preferred addition amount of Al-10RE master alloy is 3%. The effect of Sr modification on the elongation of AlSi7Cu2Mg alloy was studied. The best modification process of Al-Si alloy was obtained: 0.04% of Sr addition, 60 minutes of standing time, and 750°C of aluminum liquid temperature.
The reason for this is that rare earth intermetallic compounds are not formed when the amount of rare earth is small, and the amount of rare earth intermetallic compounds can be significantly increased when the addition amount is sufficient to produce metal fiber structures and solid solution strengthening phases of intermetallic compounds and eutectic compounds. High temperature performance. Excessive rare earth will aggravate the accumulation of RE-rich phase and become inclusions, thereby reducing the fluidity of the alloy melt.
3. Effect of metamorphic process The metamorphic process directly affects the metamorphic effect of rare earth elements. For Al-Si alloys, the key to obtaining a stable metamorphic structure is to reduce the burning loss of rare earths and prevent segregation of rare earths, so that the rare earths diffuse rapidly and evenly into the aluminum liquid. Rare earth metamorphism has a latent period, that is, it must be maintained at high temperatures for a certain period of time, rare earth can play a greater metamorphism. Under the cooling conditions of the gold mold, the incubation period of Al-Si alloy is 1-2h, and it shortens with increasing temperature. The length of the incubation period mainly depends on the diffusion rate of the rare earth in the aluminum liquid. In the production, the appropriate holding temperature and holding time can be selected according to the length of time between the modification and the casting, so as to achieve better metamorphism during casting. In studies, Zhang Weiwen et al. found that eutectic Al-Si alloys exhibit incomplete eutectic structure when rare earth metamorphism occurs. At the same time, it further explored the mechanism of its production, pointing out that in order to homogenize the microstructure of the alloy, the primary crystal should be uniformly distributed, and eutectic Si must be suppressed as the leading phase. This can be taken to increase the cooling rate, stir the melt and other measures.
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Factors affecting the effect of rare earth elements in aluminum alloys