Study on the composition optimization and microstructure properties of super high-strength aluminum alloy with scandium

With Al-8.67Zn-2.5Mg-2.5Cu aluminum alloy as the research object, using Jmatpro software to simulate and calculate the alloy phase diagram and properties, the optimal amount of Sc element added and its heat treatment process was determined, and alloy ingots were prepared through electric arc furnace. The influence of Sc element and solid solution aging process on the microstructure evolution of the sample was studied, and the strengthening mechanism of the alloy was explored. The results indicate that the tensile strength and hardness of the alloy were maximized when 0.25% Sc element was added, and the polarization of Al 3 Sc can be avoided. The numerically simulated hardness and tensile strength of the Al-8.67Zn-2.5Mg-2.5Cu-0.25Sc alloy are 139.13 HV and 424.12 MPa, respectively. The optimal heat treatment process for the alloy, including homogenization, solid solution, and aging, is 475 ℃/24 h+482 ℃+25 ℃/16 h. By cooling the samples at a cooling rate greater than 174.23 ℃/s and transferring them to the solid solution for less than 0.42 seconds, second-phase precipitation can be inhibited, resulting in an oversaturated solid solution. After homogenization heat treatment of the as-cast aluminum alloy, the hardness, tensile strength, and elongation are 139.86 HV, 432.1 MPa and 10.31%, respectively. After solid solution and aging, the hardness, tensile strength, and elongation of the alloy are increased by 35.42 HV, 146.6 MPa and 2.4%, respectively.