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Abstract

The effects of Yb additions (0.3 wt.% and 0.8 wt.%) on Al-6.5Si-1Zn cast alloy was investigated using optical microscopy (OM) and scanning electron microscopy (SEM/EDS) analysis. The purpose of this research is to investigate the variations occurred in Si morphology and the formation of intermetallics with different Yb additions, as well as their effect on hardness value. The experimental results indicates that the Yb affected the silicon eutectic morphology of Al-6.5Si-1Zn secondary alloy, when 0.8 wt.% was added to the alloy and the coarse plate Si was modified into a fine fibrous structure. Two kinds of Yb-rich intermetallics were found, such as AlSiYb and AlSiYbMg. The hardness measurements revealed that the hardness values of base alloy were higher with the Yb addition.