Manufacturing of complex components with thin walls (<3 mm) by high-pressure die castingCasting (HPDC) is increasingly demanded in automotiveAutomotive industryIndustry to consolidate parts and reduce cost. Because these castingsCasting are often used in structural applications with higher mechanical requirements, there is a desire to develop more castable, high-strength HPDC Al alloysAl alloy. In this study, the microstructuresMicrostructure of two Al7SiMgFeMn thin-wall plates with low and high (0.012 and 0.5 wt.%) Cu additionsCu addition were examined by scanning electron microscopyElectron microscopy (SEM) and transmissionTransmission election microscopy electron microscopyElectron microscopy (TEM). TEM specimens were prepared with a focused ion beam (FIB) to focus specifically on the skin region of the plates. In the low-Cu alloy, (MnFe)-rich α and Mg-rich π were predominant intermetallicIntermetallic compounds between Al dendritesDendrites and Al–Si eutectic. Upon higher Cu additionCu addition, the size of Al dendriteDendrites was clearly smaller in the high-Cu alloy. Both α and π compounds were smaller in size but higher in number density. An additional Cu-rich layer was frequently evident covering the α phase. The eutectic network was more dense, homogeneous, and interconnected between smaller Al dendritesDendrites. The influence of Cu additionsCu addition on solidificationSolidification sequence and phase formation will be discussed.