Effect of Annealing on the Interfacial Structure of Aluminum-Copper Joints

Abstract

The aim of this study is to investigate the structure development and growth kinetics of the interfacial structure of cold roll bonded Al/Cu bimetal sheet. An interfacial structure is developed during the annealing process. The characteristics of the constituent phases at the interface of Al/Cu bimetal are studied by means of scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM). The results indicate that an obvious multi-layers interdiffusion structure is developed at the Al/Cu interface. The diffusion layer is consisted of four intermetallic compounds; Al 2 Cu, AlCu, Al 3 Cu 4 and Al 4 Cu 9 . The growth of these intermetallics during annealing can be achieved by the diffusion process. The activation energies of Al 2 Cu, AlCu + Al 3 Cu 4 , Al 4 Cu 9 and the total intermetallic layer are found to be 97.504, 107.46, 117.52 and 107.85 kJ/mol, respectively. These intermetallics generally possess higher hardness values than those of the corresponding base metals. AlCu and Al 3 Cu 4 exhibit much higher hardness than that of Al 2 Cu and Al 4 Cu 9 , which implies lower fracture toughness. The observation of crack propagation paths shows that fracture mainly occurs in the intermetallic compound layers of AlCu and Al 3 Cu 4 , which are located between Al 2 Cu and Al 4 Cu 9 .

Effects of Vibration Amplitude on Microstructure Evolution and Mechanical Strength of Ultrasonic Spot Welded Cu/Al Joints

“…The effects of lattice defects generated by the severe plastic deformation on the diffusion were significantly suppressed by the non-deforming intermetallic layer. However, since the main IMC phase (CuAl 2 ) was of tetragonal structure, including a lot of structural defects, such as grain boundary and dislocations [24], it was unlikely that the effects were completely eliminated in the Cu or Al matrix junction subsequently to the reaction layer becoming continuous. Therefore, it was found that the growth rate of the intermetallic thickness was still more than 14 times greater than the rate acquired from the parabolic growth predictions made with growth rate constant, as obtained from the static heat treatments condition.…”

Interfacial Characterization and Bonding Properties of Copper/Aluminum Clad Sheets Processed by Horizontal Twin-Roll Casting, Multi-Pass Rolling, and Annealing

“…The thickness of the clad sheet interface is approximately 9 µm to 10 µm. Studies have shown that several intermetallic compound (IMC) layers can form with Cu and Al on the contact surface under the effect of thermal diffusion [18][19][20]. The EDS results (Table 2) show that the compositions of the three layers, arranged in a sequence from Al to Cu, correspond to the probable Al 2 Cu, AlCu, and Al 4 Cu 9 phases, respectively.…”

The effect of annealing on structure and hardness of (Fe-Cr)-50 at.% Al coatings synthesized by mechanical alloying

“…Previous study has reported that the refinement of coating grains can improve the hardness of coating [1]. In addition, the formation of intermetallic phases strongly affects the hardness of the sample [9,11].…”