Diffusion bonding in ultra fine-grained Al–Fe alloy indicating high-strain-rate superplasticity Original Research Article

The high temperature deformation mechanism and the diffusion bonding process were investigated on a nanocrystalline Al–Fe alloy having ultra fine grain sizes of 100 nm, produced by physical vapor deposition (PVD). Tensile tests revealed that the dominant deformation mechanism of the nanocrystalline material was cooperative grain boundary sliding accommodated by slip, which is controlled by lattice diffusion. The constitutive equation could be developed on Al based alloys having fine grain sizes of <1 μm. In addition, the present material was successfully diffusion bonded at the superplastic temperature by selecting appropriate pressure and time. The maximum lap shear strength of 88.7 MPa, which was corresponding to 83% of the parent material, was achieved at the material processed at a bonding pressure of 20 MPa in a bonding time of 1.8 ks at a temperature of 673 K. The diffusion bonding temperature on Al–Fe alloy was far lower than that on conventional superplastic aluminum alloys. The reduction in diffusion bonding temperature may be attributed to the very fine grain size.