Effects of Mn on the crystal structure of α-Al(Mn,Fe)Si particles in A356 alloys

In a commercial Al-7.0Si-0.38Mg cast alloy (A356) with 0.20 wt% Fe, added Mn modifies acicular β-Al5FeSi particles to less acicular α-Al(Mn,Fe)Si in both crystallization and precipitation conditions. The crystal structure of α-Al(Mn,Fe)Si changes from body-centered cubic (bcc)/ simple cubic (sc) to Pm3 structures in response to an increase in the bulk Mn content of the alloy. The α-Al(Mn,Fe)Si particles (50–200 nm) precipitate during solution treatment and their precipitation temperature is about 485 °C in the as-cast condition.