Interactive effects of grain refinement, eutectic modification and solidification rate on tensile properties of Al-10Si alloy

This study aims to clarify the effect of grain size and Si modification on the microstructure and tensile properties of the Al-10Si cast alloy, solidified under various cooling rates. To replicate the effect of cooling rate, directionally solidified samples were produced by remelting of the as-cast cylindrical bars. Tensile properties, grain sizes, Si modification level and chemical composition profiles were evaluated. Results showed that fast cooling rates alone, without the addition of grain refiners (Al-5Ti-1B master alloy), did not lead to equiaxed grain morphologies. On the other hand, for the slowest cooling rate tested, combined additions of the Al-5Ti-1B and the Al-10Sr master alloys resulted in equiaxed grain structures while addition of only grain refiner resulted in columnar grains. The combined additions effectively produced an equiaxed grain structure at all cooling rates tested, and further improved the tensile properties.