The measured densities of the alloys are close to the theoretical values, which indicate that the samples were free from porosity. The microstructures of the Al–7Si and Al–7Si–2.5Cu cast alloys before and after grain refinement, modification and combined addition of both refiner and modifier are shown in Fig. 1(a–g). It is observed that; refinement, modification and combined addition of both refiners and modifiers have profound influence on microstructures of the Al–7Si and Al–7Si–2.5Cu cast alloys. Alloys without any grain refiner addition have the maximum grain size (220 μm). The present experimental results confirmed that, the addition of grain refiner Al–1Ti–3B to Al–7Si or Al–7Si–2.5Cu alloy significantly refines the coarse columnar primary α´-Al grains to fine equiaxed α´-Al grains (60 μm) due to the presence of AlB2/TiB2 particles present in the master alloy (Al–1Ti–3B) which are nucleating agents during the solidification of α´-Al grains, while the eutectic silicon particles appear to be unaffected as expected. Also the addition of modifier (Sr) to Al–7Si or Al–7Si–2.5Cu cast alloy changes the plate like eutectic silicon to fine particles and fine CuAl2 particles in the interdendritic region