Impact Toughness Enhancement of Melt Treated Al-Si-Mg Cast Alloy

The alloy toughness is influenced by the alloy composition and the melt treatments applied. The present work investigates the effects of different types of grain refiners on the impact properties of Sr-modified A356.2 alloys in as-cast and heated-treated conditions. The results show that the addition of Ti and B greatly improves the alloy toughness but only in a fully modified state, and the right type of master alloy and addition levels are used. The highest values for total absorbed energy of T6-tempered alloys are obtained after using Al-5%Ti-1%B and Al-10%Ti master alloys following upon the addition of 0.04% Ti. A significant deterioration in impact properties is observed due to the Sr-B interaction in some cases. The improvements in toughness may be attributed primarily to the change in silicon particle morphology and to the dissolution and fragmentation of a number of the intermetallics formed during the T6 temper.