The effect of squeeze casting pressure and iron content on the impact energy of Al7Si0.7Mg alloy

Impact energy was evaluated for castings of Al7Si0.7Mg(0.1–0.6)Fe alloys produced using an indirect squeeze casting machine. In the as-cast condition, increases in the secondary dendrite arm spacing (DAS), the centre-to-centre distance (λSi) between silicon particles, and the presence of macrosegregation (eutectic concentration on a macro-scale) all led to a decrease in the impact energy. Failure was found to be by fracture through the interdendritic and macrosegregated eutectic regions. An increase in squeeze pressure in the range of 30–100 MPa during solidification did not have a direct influence on the impact energy of the castings. In the T6 condition, the variation in the size and shape of silicon particles throughout the castings was quite small, corresponding to only a small variation in impact energy. An increase in iron content, which increased the size of β-phase particles, decreased the impact energy in both as-cast and T6 heat treated samples. This effect was greater in the low iron range (0.12–0.35 wt.%) in the as-cast condition.