Microstructure, mechanical properties and corrosion behaviour of Ti6Al4V/Al2O3 joints brazed with TiCuNi filler

Abstract

Ti6Al4V and Al2O3 were successfully vacuum brazed at 980 °C using TiCuNi filler foil. The microstructure and the chemical composition of the interface were analysed by SEM (scanning electron microscopy) and EDS (energy dispersive spectros- copy), respectively. The hardness profile across the interface and the mechanical strength of joints were assessed by Vickers microhardness tests and shear tests, respectively. The fracture surfaces were analysed by SEM, EDS and XRD (X-ray dif- fraction). The corrosion behaviour of joints was evaluated by OCP (open circuit potential), potentiodynamic polarisation tests and EIS (electrochemical impedance spectroscopy). Brazing produced a layered interface, free of pores and cracks, essentially composed of α-Ti, Ti2(Cu,Ni) and TixOy. The shear strength of joints was 168 ± 13 MPa, and fracture occurred partially through the hardest zone of the interface (1261 HV0.01.), located in the vicinity of the Al2O3 sample, and partially through the ceramic sample. The brazed joint did not significantly affect the corrosion behaviour of Ti6Al4V.