Microstructures and mechanical properties of brazed 6063 aluminum alloy joint with Al-Cu-Si-Ni filler metal

Research on a Low Melting Point Al-Si-Cu (Ni) Filler Metal for 6063 Aluminum Alloy Brazing

“…Figure 12a shows that the shear strength of the Al-6.5Si-20Cu brazed joint was approximately 117.2 MPa, and the shear strength of the Al-6.5Si-20Cu-(1.0, 1.5, 2.0) Ni 12b shows the microhardness curve of the brazed joints. There were Al2Cu intermetallic compounds and primary Si in the brazed seam center area of the weld [2,7,25], and the hardness of this zone was 281~310 HV. During the brazing process, the elements between the filler metal and the base metal diffused to form a diffusion zone whose hardness was slightly higher than that of the base metal.…”

“…Brazing holds the advantages of low deformation of the weldment, high dimensional accuracy, and high production efficiency. Brazing is one of the commonly used connection methods for heat exchangers [1][2][3]. As a light alloy material with excellent weldability and heat conductivity, 6063 aluminum alloy can be used as the main material of the heat exchanger [4][5][6].…”

“…The content of Si is 7~13 wt.%, and the liquidus temperature is approximately 570 • C [7,8]. To obtain excellent brazed joints, the brazing temperature must be higher than 595 • C, which is close to the solid phase temperature of 6063 aluminum alloy (approximately 615 • C), which may cause base metal grain growth or over-burning [2,4,7]. In addition, an excessive brazing temperature not only enhances the manufacturing cost but also causes dissolution of the base metal, and the quality of the brazed joint obtained is poor [5,9].…”

“…To solve the problem of an excessively high brazing temperature, in recent years, many researchers have developed a series of new low melting point, aluminum-based filler metals by alloying methods with the theoretical support of eutectic components of Al-Si, 2 of 14 Al-Cu, Al-Ge, Al-Zn, etc., and the corresponding properties have been studied [2,7,[10][11][12]. The addition of Ge to the Al-Si filler metal can narrow the melting point of the Al-Si-Ge filler metal, but the melting range of the filler metal will widen with increasing Ge content, and the fluidity of the filler metal will decrease.…”

“…The results indicate that adding an appropriate amount of Ni to Al-Si-Cu filler metal can replace part of the Cu and reduce the adverse effect of θ(Al 2 Cu) on joint properties [4,5,14]. Luo et al [4] developed Al-10Si-15Cu-4Ni filler metal with a melting range of 24.9 • C and successfully brazed 6061 aluminum alloy at 570 • C. Meanwhile, the joint shear strength was as high as 144.4 MPa, which was higher than that of Al-Si-Cu brazing filler metal [2,7]. However, Al-Si-Cu filler metal still has the problems of a wide melting interval and a low shear strength of the brazed joint, which urgently needs to be solved.…”