Interface characterization of Al/cast iron composite

In this article, interface characteristics of aluminum and cast iron bimetal has been investigated. To reach an acceptable composite products, from two materials, interface characteristics needs to be investigated. Aluminum melt was poured, at 700 and 750 ̊C, around cylindrical cast iron bars having melt/solid volume ratios of 3, 5 and 8, respectively. Optical and SEM microscopic observations showed that a reaction layer may form at the interface. This layer is composed of Fe2Al5 intermetallic which forms initially at the rough surface of the insert after making contact with molten metal. Microstructural analysis showed the increasing of temperature and the Vm/Vs ratio leads to formation of a thicker and more uniform intermetallic layer. Microhardness of the Fe2Al5 was 824 HV and the thickness of interaction layer varied from 5μm, for the sample produced at 700 ̊C and 3 Vm/Vs, up to 20μm for the sample poured at 750 ̊C and 8 Vm/Vs. A mechanism is suggested for nucleation and growth of this intermetallic layer and also graphite engulfment of gray cast iron, by aluminum melt, at the interface of two metals.