Transient Liquid-Phase Diffusion Bonding of Aluminum Metal Matrix Composite Using a Mixed Cu-Ni Powder Interlayer

摘要

In the present study, the transient liquid-phase diffusion bonding of an aluminum metal matrix composite (6061-15 wt.% SiCp) has been investigated for the first time using a mixed Cu-Ni powder interlayer at 560℃, 0.2 MPa, for different holding times up to 6 h. The microstructure of the isothermally solidified zone contains equilibrium precipitate CuAl_2, metastable precipitate Al_9Ni_2 in the matrix of α-solid solution along with the reinforcement particles (SiC). On the other hand, the microstructure of the central bond zone consists of equilibrium phases such as NiAl_3, Al_7Cu_4Ni and α-solid solution along with SiC particles (without any segregation) and the presence of microporosities. During shear test, the crack originates from microporosities and propagates along the interphase interfaces resulting in poor bond strength for lower holding times. As the bonding time increases, with continual diffusion, the structural heterogeneity is diminished, and the microporosities are eliminated at the central bond zone. Accordingly, after 6-h holding, the microstructure of the central bond zone mainly consists of NiAl_3 without any visible microporosity. This provides a joint efficiency of 84% with failure primarily occurring through decohesion at the SiC particle/matrix interface.