What are the roles of copper and silicon in aluminum alloys?

What are the roles of copper and silicon in aluminum alloys? Today we are going to give a basic introduction to this topic as a professional manufacturer of aluminum products.

Copper element Cu

When the aluminum-copper alloy is rich in aluminum-rich part 548, the maximum solubility of copper in aluminum is 5.65%, and when the temperature drops to 302, the solubility of copper is 0.45%. Copper is an important alloying element, which has a certain solid solution strengthening effect, and CuAl2 precipitated by aging has obvious aging strengthening effect. The copper content in aluminum alloy is usually 2.5%~5%, and the strengthening effect is best when the copper content is 4%~6.8%, so the copper content of most duralumin alloys is in this range.

Aluminum-copper alloys can contain less silicon, magnesium, manganese, chromium, zinc, iron and other elements.

Silicon element Si

When the eutectic temperature of the aluminum-rich part of the Al-Si alloy is 577, the maximum solubility of silicon in the solid solution is 1.65%. Although solubility decreases with decreasing temperature, such alloys are generally not heat-treated to strengthen. Aluminum-silicon alloys have excellent casting properties and corrosion resistance.

If magnesium and silicon are added to aluminum at the same time to form an aluminum-magnesium-silicon alloy, the strengthening phase is MgSi. The mass ratio of magnesium to silicon is 1.73:1. When designing the composition of Al-Mg-Si alloys, the content of magnesium and silicon is configured in this ratio on the matrix. Some Al-Mg-Si alloys, in order to improve the strength, add an appropriate amount of copper, and at the same time add an appropriate amount of chromium to offset the adverse effects of copper corrosion resistance.

The maximum solubility of the aluminum-rich part of Mg2Si in aluminum is 1.85% in the equilibrium phase diagram of Al-Mg2Si alloy alloy, and the deceleration is small with the decrease of temperature. In deformed aluminum alloys, silicon alone added to aluminum is limited to welding materials, and silicon added to aluminum also has a certain strengthening effect.