Intermetallics Formation during Solidification of Al-Si-Cu-Mg Cast Alloys

The present study was undertaken to examine the effect of iron, manganese, copper and magnesium on the microstructural characteristics of Al-11%Si-2%Cu-Mg-based alloy referred to as 396 under different working conditions. The results show that strontium (Sr) has high affinity to react with magnesium (Mg), resulting in reduced effectiveness as eutectic silicon modifier or age hardening agent. In addition, Sr alters the sequence of the precipitation of the alpha-AlFeMnSi phase from post-eutectic to pro-eutectic which would harden the soft alpha-Aluminum matrix. The mechanism is still under investigation. The interactions between iron (Fe) and Mg and Sr-Mg result in the formation of serval dissolvable intermetallics during the solutionizing treatment such as beta-AlFeSi, pi-AlFeMgSi and Q-AlMgSiCu phases. The study also emphasizes the role of modification and grain refining as well as intermetallics in porosity formation and hardness of samples aged in the temperature range 155-240 degrees C.

Automated summary

This study investigated the effect of iron, manganese, copper, and magnesium on the microstructural characteristics of Al-11%Si-2%Cu-Mg-based alloy. The study found that strontium has a high affinity to react with magnesium, reducing its effectiveness as a silicon modifier or age hardening agent. The interaction between iron and magnesium, as well as strontium-magnesium, resulted in the formation of several dissolvable intermetallic compounds.