Structure and properties of Al–7Si–Ni and Al–7Si–Cu cast alloys nonmodified and modified with Sr

This work shows the results obtained of the microstructural analysis by optical microscopy (OM) and scanning electron microscopy (SEM-EDX) and its relationship with the mechanical properties of Al–7Si–0.5Cu, Al–7Si–1.5Cu, Al–7Si–0.5Ni and Al–7Si–1.0Ni cast alloys. These cast alloys were manufactured in two conditions: nonmodified and modified with 0.02 wt.% Sr, in order to evaluate the effect of the Sr on the eutectic phase morphology. Results indicated that Sr presence produce a good modification rating of the eutectic phase in the case of Al–7Si–Cu cast alloys and their mechanical properties were increased in as cast condition. However the massive eutectic microconstituent NiAl3 of Al–Si–Ni cast alloys was not affected by Sr presence, and their mechanical properties were not improved.