Abstract: In order to change the size, morphology and distribution of the secondary phase and improve the electrical and mechanical properties of the Ai-Si alloy, Al-4Si and Al-4Si-0.2Er alloys were prepared by selecting rare earth element Er as the alloying element, and the effect of rare earth Er and homogenization on the microstructure, electrical and mechanical properties of the as-extruded Al-4Si and Al-4Si-0.2Er alloys was studied. The results show that rare earth Er is beneficial to promote the precipitation of Si from solid solution and the formation of new phase ErSi₂, which increases the number of the secondary phase in the alloy and results in obvious dispersion strengthening effect, so that the mechanical properties of the alloy are improved, with the conductivity keeps stable. When homogenized at 540 ℃ for 1 h then furnace-cooled, the Al-4Si-0.2Er alloy has better comprehensive performance, where the homogenization treatment promotes the secondary phase to be precipitated with finer size and dispersed in a granular form. Meanwhile, the conductivity of the Al-4Si-0.2Er alloy is increased from 51.61%IACS in the extruded state to 56.44%IACS, which is 9.4% higher. The furnace cooling process results in a slight decrease of mechanical properties of the Al-4Si-0.2Er alloy, with tensile strength of 87.80 MPa, elongation of 35.9%, and hardness of 36.00 HV0.3.

Key words: rare earth Er, homogenization treatment, Al-Si alloy, conductivity