The Role of Eutectic Silicon Morphology in the Machinability of Cast Al-Si Alloys

Recycled Al alloys are of major interest in the automotive industry due to their significantly lower production energy requirements compared to primary alloys. Consequently, the machinability of recycled Al alloys is of paramount importance, as components must be machined to achieve the desired final shape. To investigate this, Al-Si specimens, with Si content between 7% and 10%, obtained by casting were analysed to correlate the effect of the microstructure with machinability. The bulk and surface characteristics of turned specimens were evaluated using optical and scanning electron microscopy, profilometry, microhardness tests, electron back-scattered diffraction and corrosion experiments. The main results indicated that the eutectic Si morphology represents a key parameter influencing the surface tearing frequency of the turned specimens.