| Conductor materials not only have a good electrical conductivity, but also have good strength to support their own weight and external natural load. Al-Mg-Si alloy has good mechanical properties, so it is widely used in heavy icing area and long crossing lines. However Al-Mg-Si alloy has some problems, such as low electrical conductivity; Mg2 Si phase is dendrite, which is bad for mechanical properties, especially ductility; coarse grains in cast microstructure, and mechanical properties is to be improved.In the paper, the addition of Rare earth, boron and strontium in the Al-Mg-Si alloy6201, 6101, is to improve the electrical conductivity. Orthogonal experiment is applied to optimize the composition of Al-Mg-Si-B-Re-Sr alloy. Electrical conductor, tensile strength and elongation are tested, and Al-0.96Mg-0.6Si-0.05B-0.3Re-0.03 Sr alloy was prepared. Homogenize the alloy ingot at different temperatures, and research effect of homogenization on microstructure and properties, and determine the best homogenization is 575℃,9h. After homogenization, aluminum alloy wire was prepared by extrusion and drawing. Test the final properties of the wire after solid solution and aging.The result showed that, the influencing degree of each factor that affect electrical conductivity of the alloy is as follows: the ratio of magnesium and silicon, the content of boron, the content of strontium and the content of rare earth. The significant degree of influence on tensile strength is in order: the ratio of magnesium and silicon, the content of strontium, the content of boron and the content of rare earth. While the significant degree of influence on elongation is in order: the ratio of magnesium and silicon, the content of boron, the content of strontium and the content of rare earth. Electrical conductor, tensile strength and elongation of the cast alloy Al-0.96Mg-0.6Si-0.05B-0.3Re-0.03 Sr, which is prepared in accordance with the optimal scheme, is 43.1%IACS,175 MPa, 12.9%.When the ratio of magnesium and silicon is 1.5:1, primary silicon in thick plate is produced. Primary silicon in thick plate leads to lower conductivity, tensile strength and elongation. When the ratio of magnesium and silicon is 1.6:1 or 1.7:1, no primary silicon appear. The mass fraction of 0.03% strontium can make Mg2 Si network dispersion, fine, and make β-Al Fe Si convert to α-Al Fe Si, which is good to the mechanical properties and processing performance of the alloy. When the content of strontium is more than 0.1%, Al4 Sr phase in needle appear in the alloy. With increasing of content of strontium, more Al4 Sr phase was formed, and segregate at the grain boundaries, reducing conductivity and mechanical properties of the alloy.Homogenization in different temperature is used to the optimum alloy, when 560℃, 16 h or 575℃, 9h, segregation at grain boundaries has been significantly improved, the grain boundary become thinning, the second phase is dispersed. While 590℃, 16 h, burning phenomenon of alloy occur. When the temperature is 560℃, keeping 16 hours, the electrical conductivity reaches a maximum of 55.6%ACS, 29.0% more than that of the cast alloy(43.1%IACS). While the temperature is 575℃, keeping 9 hours, the electrical conductivity reaches a maximum of 55.5%ACS, 28.7% more than that of the cast alloy(43.1%IACS). After the homogenization treatment, the tensile strength of alloy decreases, but elongation increased. When the temperature is 560℃, keeping 16 hours, the tensile strength is 153 MPa, elongation is 13.1%. While the temperature is 575℃, keeping 9 hours, the tensile strength is 166 MPa, elongation is 13%.After extrusion, grain of Al-0.96Mg-0.6Si-0.05B-0.3Re-0.03 Sr was elongated, with obvious directivity along the extrusion direction. The second phase in grain boundary is broken and distributed in obvious fibrous. By drawing at room temperature, the microstructure of aluminum wire is vimineous grain as fibril shape. After intermediate annealing of 350 ℃, microstructure of the alloy does not change significantly, and electrical conductivity and tensile strength decrease than that of the unannealed, but elongation increase.With aging time increasing, the tensile strength of alloy wire decrease after rising first, and higher aging temperature, the peak value of tensile strength is larger, the time needed for peak is shorter. With higher aging temperature and longer aging time, the conductivity of alloy wire gradually increases. The best processing is solution in 550℃ for half an hour, then cool in air, and aging in 200℃ for 12 hours. Then the performance of the aluminum wire is best, tensile strength, elongation and conductivity is respectively 294 MPa, 10%, 53.9% IACS. |
PDF Full Text Request