ON THE INTERFACIAL CHARACTERISTICS OF COMPOUND CAST Al/BRASS BIMETALS

The interface characteristics of aluminum/brass bimetals produced by compound casting were investigated. Aluminum melt was poured into molds, at 700 and 750 A degrees C, around cylindrical brass bars having melt-to-solid volume ratios of 3 and 5. Macroscopic studies showed that a solid ring is formed around the solid core, which was clearly visible after cutting the casting. X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies confirmed that various layers could be distinguished, for example, CuZn, Al4Cu3Zn, Al2Cu, eutectics of alpha-Al/Al2Cu, and Al dendrites in the vicinity of the solidified aluminum melt. The hardness of intermetallic layers was 513, 477, and 650 Vickers, respectively, from the center brass core to the aluminum outer ring. Existence of microscopic pores and cavities in the eutectic and dendritic layers was noticed after examination. Some of these pores are possibly the result of bubble entrapment. The formation of Al2Cu and Al4Cu3Zn layers prevented solid solutions from being saturated by copper, which can be one reason why Cu4Al9 did not appear in the couples produced by this method.