Iron is a common and deleterious impurity in Al-Si foundry alloys. Pre-eutectic beta-Al_5FeSi platelets have been associated with an increase in porosity. The addition of Mn to Al-Si foundry alloys containing iron has been suggested to reduce porosity by altering the intermetallic phase to alpha-Al_(15)(Fe, Mn)_3Si_2. The addition of Mn to Al-9 percent Si-x percent Cu-0.5 percent Mg-y percent Fe alloys, to a Fe:Mn ratio of 2:1, reduces the amount and variability of porosity in sand-cast plates. The effect is most significant for alloys with high iron levels (1 wt percent) and no copper addition. The reduction is not as significant at lower iron levels (0.6 percent) or higher copper levels (3 percent).
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