The type of Fe- and Mn-bearing particles in Al-7%Si foundry alloys, and the effect on the brittleness

Increasing Fe-content in Al7%Si-0.14%Mg was found to give more brittle material. Additions of 0.6% Mn improved the fracture toughness in most of the cases. The same additions did not improve the elongation, except for one of the alloys. The Alstruc microstructure solidification program can to some extent predict when Chinese script a-AlFeSi particles are formed, and when plates of β-Al-FeSi are formed, based on the composition of the alloy and the rate of cooling. It can also predict the volume fraction of intermetallic particles, and the fraction liquid that had solidified when the first particles began to form. The Alstruc simulations are compared with metallographic observations, and both are used to discuss the brittleness of the alloys.