An investigation of metallurgical bonding in Al–7Si/gray iron bimetal composites

Al–7Si/gray iron bimetal composites with a sound metallurgical bonding were obtained by a gravity die casting process. The surface treatments of the gray iron specimen including fluxing and hot dipping were applied to forming a complete metallurgical bonding layer at the Al–7Si/gray iron interface. In addition, the effect of Mn in dipping bath on the microstructure of the Al–7Si/gray iron interfacial bond zone has been studied in an Al–7Si alloy containing five different levels of Mn ranging from 0 to 5 wt%. Microstructure analysis indicates that addition of Mn in dipping bath can eliminate the harmful needle-like phase (β-Al5FeSi) as the Mn content is no less than 1.5 wt% and also plays an important role in facilitating the growth of intermetallic phases [α-Al15(FexMn1−x)3Si2] and the metallurgical bonding layer. The sound metallurgical bonding formed at the Al–7Si/gray iron interface is attributed to combining the effect of surface treatments and selection of Mn content.