Influence Of Alternating Magnetic-Field On Microstructures And Property Of Al-Mg₂Si Alloy

Al-Mg₂Si alloy is a kind of false binary eutectic alloy material having a great developing future. The influence of content of intermetallic compound Mg₂Si, technological parameters of electromagnetic stirring, alloy elements and heat-treatment on microstructures of hyper-eutectic Mg₂Si alloy and its mechanical properties was taken as the research object in this paper. The processing principle was also discussed.It is found from the experimental results that the volumetric fraction of primary Mg₂Si in the Al-Mg₂Si alloy increases and the dimension of crystal grains increase and became irregular lumped, with the increases of content of Mg₂Si. The general mechanical properties of alloy are excellent under the condition that the content of Mg₂Si was within the range of 15%—35%.Electromagnetic stirring can improve microstructures and mechanical properties of Al-Mg₂Si alloy to a certain extent. On condition that density of alternating magnetic-field is between 100G and 120G (Al-18Mg₂Si alloy only) or between 120G and HOG (Al-30Mg₂Si alloy only) and stirring duration is 60s, and at a proper cooling condition, alloy microstructures acquired is finer relatively, and mechanical properties has improved to some extent.Alloy elements also improve the microstructures and mechanical properties of Al-Mg₂Si alloy to a great extent. The fining effect is best when input of Element P is controlled at 0.7%—1.1% and head preservation duration is 15min. On this condition, primary Mg₂Si is finest, most regular and uniformly distributed. The mechanical properties of alloy are better. The fining effect is better when input of Element Ti is controlled at 0.5% and head preservation duration is 20min. On this condition, the primary is finer relatively but the distribution is not uniform. The mechanical properties have also improved. As a whole, Element Ti and its effect is not remarkable as that of Element P.During heat-treatment, the Al-Mg₂Si alloy after electromagnetic stirring separates continuously out dispersive and fine Mg₂Si grains, and the tiered and sliced Mg₂Si disappears, along with prolonging the heat reservation duration of solution heat treatment; the primary shape and distribution does not show evident change; meanwhile, both alloy hardness and tensile strength increase sharply first and then decrease gently, and the extensibility always declines. To Al-Mg₂Si alloy after electromagnetic stirring, the most suitable heat reservation duration of solution heat treatment is 6h during heat-treatment. On this condition, the alloy microstructures and mechanical properties are best.