Metallurgical process analysis and microstructure characterization of the bonding interface of QAl9-4 aluminum bronze and 304 stainless steel composite materials

QAl9-4 aluminum bronze and 304 stainless steel composites were fabricated by vacuum smelting-casting at 1150 degrees C, in a vacuum of 4.0 x 10(-2) Pa. Microstructure and chemical composition were characterized by using transmission electron microscopy (TEM), X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). Properties of interface were studied by shear tests and hardness measurement. Between the QAl9-4 aluminum bronze and 304 stainless steel, a transition zone that the width is about 133 mu m and the maximum micro-hardness value is 467 HV was observed. It is much higher than that of QAl9-4 aluminum bronze and 304 stainless steel, the main reason is considered to the formation of the brittle intermetallic compounds such as AlCrFe2, Al4Cu9 and AlNi3, but these intermetallic compounds are very easy to cause the interfacial fracture. The interfacial shape close to 304 stainless steel is flat, but to QAl9-4 aluminum bronze is zigzag. The shear strength of the composite is 278 MPa. Microstructure formation mechanism of interfacial layer can be mainly considered as Fe, Cr atoms of steel substrate are given a priority in molten copper liquid compared with impurity elements (Mn, Si), eventually forming a good metallurgical bonding state on both sides of the substrate through inter-diffusion of interfacial atoms. (C) 2016 Elsevier B.V. All rights reserved.