AlSi10Mg alloys are ideal candidates for engine housings of electrical cars due to their good castability. Mechanical properties can be improved with the addition of Cu, but the precipitation sequence of AlSi10MgCuX alloys is still a topic of study. Furthermore, the increasing importance of green production of cast parts by increasing the recycling fraction of aluminum results in a high amount of iron (about 0.35%wt) with consequences on the mechanical properties.

In this work the influence of the copper content on the ageing properties of secondary AlSi10MgCuX alloys were investigated by using five different alloys with 0, 0.4, 0.8, 1.2 and 2.0 wt.% copper. This was done by firstly performing a solution heat treatment at 530°C for 4h for the alloys with low content of Cu and a two-step solution heat treatment for higher content of Cu due to the decreased melting point. Metallography was carried out to identify the primary phases present after the solution heat treatment. The ageing treatments were done at 170, 180, and 200°C for up to 100 hours. Following the heat treatment, the ageing curves were determined by microhardness measurements. As already shown in former studies the increase in copper lead to an increase in maximum hardness due to the formation of the θ-phase and the transition of the main precipitate from β`` to the θ and Q family for alloys containing more than 0.4 % copper. Moreover, the peak ageing times were increased with increasing copper content.

The addition of copper modifies the precipitation sequence and kinetics, which in consequence leads to a change in the main precipitates and an increase in maximum hardness.