Reactive Interaction and Wetting of Fe‐ and Mn‐Containing, Secondary AlSi Alloys with Manganese Oxide Ceramic Filter Material for Fe Removal

Fe is an impurity element in secondary, i.e., recycled AlSi‐cast alloys deteriorating castability and mechanical properties due to formation of intermetallic particles. Fe removal can be achieved by binding Fe into Fe‐containing, primary intermetallic particles and removing these, subsequently, from the Fe‐depleted AlSi alloy melt. In the process, Mn enhances formation of these primary intermetallic particles. The present study investigates the potential of Mn oxide as ceramic filter material for Fe removal upon interaction of purifying substrates with the secondary AlSi‐cast alloys Al7.1Si1.5Fe, Al7.1Si1.175Fe0.375Mn, and Al7.1Si0.75Fe0.75Mn. Sessile‐drop and crucible experiments are analyzed regarding wettability, chemical interaction, primary particle formation, and the effect on alloy composition and microstructure after solidification. The Mn oxide forms a reactive system with the AlSi alloys. The very poor‐wetting Mn oxide is reduced via aluminothermic reaction forming poor‐wetting Al 2 O 3 while Mn enriches in the alloy. The primary Fe‐containing particles are preferentially attached to the Mn oxide. The remaining Fe content of the AlSi melt is reduced below the initially thermodynamically expected value due to additional Mn from the Mn oxide. The reduction of the Fe and also Mn content in the remaining alloy without primary particles manifests in microstructures with a lower intermetallic phase volume.