<p>The effects of strengthening elements (Mg, Cu, or Mg + Cu) and the corresponding precipitate phases on the balance between electrical conductivity and hardness in Al-6.5Si alloy were investigated. It is indicated that with the increasing of element additions, the hardness increases but the electrical conductivity decreases. However, the ability of precipitates generated by different element addition to balance these two properties varies. Specifically, the Q′ phase (the primary precipitate in Al-Si-Mg-Cu alloys) is characterized by uniformly distributed fine spherical particles with smooth interfaces and the highest number density.&#xa0;This microstructure enables strong dislocation pinning while minimizing electron scattering, thereby achieving the highest hardness and optimal electrical conductivity, which represents the most favorable balance between these properties. The β′ phase (the dominant precipitate in Al-Si-Mg alloys) exhibits a short rod-like or quasi-spherical morphology, resulting in a hardness comparable to that of the Al-Si-Mg-Cu alloys. However, the higher interfacial roughness of the β′ phase enhances electron scattering, leading to lower electrical conductivity. The θ phase (main precipitate in Al-Si-Cu alloys) features coarse plate-like structures with the lowest number density, resulting in the lowest hardness and minimum electrical conductivity, and consequently, the weakest ability to balance these properties.</p>