Aluminium-based moderate temperature filler metals for vacuum brazing of 6061 aluminium alloy

Four kinds of aluminum based moderate temperature filler metals used for vacuum brazing of 6061 aluminum alloy were prepared by rapid solidification-isothermal rolling. The effects of alloy elements content on the melting characteristics of filler metals was studied by Differential Scanning Calorimetry (DSC). The microstructures of the filler metals and brazed joints were observed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The results show that with the increase of Cu content into the filler metals,the liquid phase temperature gradually is decreased. Microstructure characterzation of the brazed joints shows the eutectic structure of (α+β) and (α+θ) decrease gradually, θ-CuAl₂(Ni) gradually increases and transforms from small fishbone shapes to block shapes. Peak shear strength of 83 MPa for the 6061 aluminum joint with Al-9.5Si-10Cu-2Ni-0.5Mg was achieved after brazing at 575℃ for 2 min.