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. (C) 2003 Elsevier Science B.V. All rights reserved.