Abstract:The electrical conductivity, mechanical property and heat resistance of Al-Mg-Si alloy with Zr adding were investigated. It is found that lower Mg-Si molar ratio in the alloy, which is lower than 2, promotes the nucleation of β″ phase and obtains fine and dispersed β″ phase, and improves the mechanical properties of the alloy. The excess Si has little adverse effect on the electrical conductivity of the alloy due to its low solubility in aluminum. As the Mg-Si molar ratio is greater than 2.5, the nucleation rate of β″ phase decreases, the particles of β″ phase are coarsened, Coarse Mg-enriched phase occurs, the mechanical properties of the alloy are deteriorated. Excess Mg is still dissolved in the base metal after aging, which increases lattice distortion level and reduces the electrical conductivity of the alloy. After adding Zr, the electrical conductivity of the alloy decreases and the tensile strength increases. Dissolved Zr atoms reduce the diffusion rate of Mg and Si atoms in the alloy. During aging, the diffusion rates of Mg and Si atoms in alloys with 0.13% Zr and 0.18% Zr are 0.92 time and 0.75 time of that diffusion rate in the alloy without Zr, respectively. Therefore, the lower diffusion rate of Mg and Si element in Al-Mg-Si-Zr alloy prolongs the nucleation incubation period of β″ phase, and hinder the growth of the β″ phase particles, which results in fine dispersed particles β″ phase; the phase transformation speed from β phase to β′ phase becomes slow; the mechanical properties and heat resistance of the alloy are enhanced.

Key words: Al-Mg-Si alloy; Zr addition; heat-resistant aluminum alloy; precipitated phase; diffusion coefficient