粉末冶金法制备AlMgSi_x高硅铝合金工艺及组织性能研究

To eliminate coarse silicon and improve relative density, AlMgSi_x (x = 10, 20, 30, 40) high-silicon aluminum alloys with different silicon contents were prepared using ball milling and hot pressing sintering. The effects of preparation process and silicon content on microstructure and properties were also investigated. The results showed that a low-energy ball milling process (ball-to-powder ratio of 6:1, speed of 220 r/min, for 6 h) uniformly mixed AlMgSi₁₀ alloy powder with silicon powder and preventing the introduction of impurities. Different sintering processes were designed based on silicon contents to achieve densification. The sintered alloy primarily consisted of α-Al, primary silicon, and a small amount of Mg₂Si. The primary silicon appeared in a flake shape and irregular interlocking morphology. The properties of alloys were dominated by the silicon content. As the silicon content increased, the elastic modulus, hardness, and compressive yield strength of the alloys improved while plasticity decreased. Specifically, the AlMgSi₂₀ alloy exhibited a yield strength of 154 MPa and did not fracture during compression. The AlMgSi₄₀ alloy achieved the highest elastic modulus and hardness, measuring 103.76 GPa and HBW 67.07, respectively. Furthermore, the AlMgSi₄₀ alloy showed the lowest thermal expansion coefficient of 12.2×10⁻⁶ K⁻¹, due to the high content of silicon which suppressed the expansion of α-Al. Additionally, the presence of silicon obstructed the interconnected aluminum structure, resulting in phonon and electron scattering, which consequently reduced the thermal conductivity of the alloy.