Rotary friction welding of pure aluminum to preheated brass

Rotary friction welding dissimilar metals of AA1100 aluminum to H59 brass was conducted with a phi 20-mm cylinder sample. The friction pressure is 90 MPa and the welding time is 15 s. Preheating to 600 K and 873 K were conducted to soften H59 brass (i.e., the hard side), so that the both metal with great differences in physical properties could deform simultaneously at the friction interface. The deformation rate was calculated by solving constitution equation, and the necessary parameter interfacial temperature was obtained by infrared thermal imaging analysis. SEM observation and EDS analysis were jointly conducted to clarify microstructure and elements distribution across the interface. The results show that the joint produced without preheating brass contain some unwelded areas and therefore presents lower tensile strength (30 MPa) just 33% of the aluminum base metal. Preheating results in large temperature difference (166 K) on both side of interface. Ratio of deformation rate psi is defined to characterize deformations' difference. psi drops two orders of magnitude (from 600 decrease to 5) when brass was preheated to 600 K, but raising preheating temperature to 873 K, its value has minor change (from 5 decrease to 1). Smaller psi value implies a comparative shear deformation and viscoplastic flow on both sides' surface. The welding interface presents layered structure, which is composed of CuAl2 + CuAl + Cu9Al4 laminate. With a thin IMCs layer (3 mu m), the joint has highest tensile strength 63 MPa.