Precipitation Sequence in an Al-Si-Mg Foundry Alloy

It is often assumed that the precipitation sequence and phases in Al-Si-Mg foundry alloys, such as A356 with 7 wt%Si, are similar to those in wrought 6xxx Al-Mg-Si alloys, such as 6063. The foundry alloys have been less extensively studied due to added difficulties in sample preparation, resulting from the high volume fraction of coarse particles of spheroidised eutectic silicon. Recent work has been successful in studying the precipitation sequence in a foundry alloy containing 0.45 wt%Mg. The work highlights some differences and similarities between foundry and wrought alloy precipitation, which may have implications for alloy design and heat-treatment.