The thermomechanical behavior of cast Al-Si piston alloys is highly dependent on the condition of the highly interconnected hybrid 3D network which is composed of primary and eutectic silicon and intermetallic phases which are found embedded in the α-Al matrix. The very similar X-ray absorption of silicon and the α-Al matrix is problematic for the local identification of these phases and thus for the accurate segmentation and characterization of all rigid phases in the network when laboratory X-ray tomographs are used. A combination of conventional X-ray computed tomography, synchrotron computed tomography, and chemical deep etching performed on the same alloy and at the same position allows for an automatic segmentation and a more accurate characterization of phases across large representative volumes and thus provides the information necessary for a quantification of the whole 3D microstructure of the alloys.