From the results obtained, it can be concluded that the inter-active effect between Bi and Sr was clearly revealed by usingcomputer aided cooling curve thermal analysis, coupled withmicrostructural inspection. The presence of Bi in the Al–Si meltappears to counteract the effect of Sr as a modifier for eutec-tic Si by increasing nucleation and growth temperatures. A newmap was established based on growth temperature, Sr/Bi ratio andmodification rating. Rational interpretation of this map showedthree distinct areas, namely unmodified, partially modified andfully modified region, limited by both temperature and Sr/Bi ratio.The map indicates that there is a threshold of Sr/Bi ratio around0.5 below which the modification effect of Sr is lost and flake-likeunmodified silicon structure is formed. This map generated reliableresults that can be used as a reference plot to estimate the siliconmorphology of fully solidified Al–Si castings. The aluminum indus-tries will most certainly benefit from this research work in termsof increased productivity, quality, costing and time savings due toincreased use of aluminum-based secondary alloys.