Microstructure evolution and mechanical properties of Mg/Al diffusion bonded joints

Mg/Al was bonded successfully via vacuum diffusion bonding in this paper. Microstructure evolution, the growth kinetic of IMCs, diffusion behaviors and mechanical properties were investigated, and their relations were discussed. The results indicate that, the multi-layer diffusion couple at the joint consisted of Al-based solid solution (α), Al3Mg2 layer (β), Al12Mg17 layer (γ), and Mg-based solid solution (δ). In addition, Mg/Al vacuum diffusion bonding was a diffusion-controlled process. Growth kinetic equations of the intermetallic phases were developed and the calculation results were in good agreement with the experimental data. The different interdiffusion coefficients calculated could characterize the nature of the differences in growth-rate. Microhardness was measured by the nanoindentation hardness tester. The result showed that the microhardness of the transition layer was higher than those of Al and Mg base metals due to intermetallic phases. Mechanical properties of the bonded joints were investigated by shear strength, the graphs of shear fracture showed a brittle fracture which occurred at the joint interface.