Micro-/nano-scale structure and elemental diffusion in the Al/Ti/Al sandwich structure

Abstract

To reveal the complexities of microstructures at the Al/Ti interface, Al/Ti/Al sandwich structures are produced through thermal pressing and annealing treatment. The multi-scale interface structures, elemental diffusion, grain characteristics, and micromechanics are investigated by scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM), and nano-indentation. The results indicate only TiAl3 is generated at the interface, and the interlayer thickness and TiAl3 grain size increase with the rising temperature. On the microscale, a compact interlayer is visible at 500 and 550 °C, whereas massive Al-enriched bulks are dispersed in the interlayer as the temperature increases to 650 °C. Abnormal micro-defects at 600 and 650 °C are partially formed with the thickening of the interlayer and the segregation of Mg and Si. Unexpectedly, interfacial microvoids, amorphous layers, and oxides are detected, which hinder the growth of the interlayer. On the nanoscale, misfit dislocations and lattice distortions are observed at the interface. More interestingly, the Ti–Al solid solution structures with severe lattice misfits are generated on the three-dimensional (3D) Ti/TiAl3 interface, which is considered to be a novel strategy for enhancing the strength-plasticity synergy of composite structures.

Keywords

• Al/Ti composite structure
• Interface microstructure
• Element diffusion
• Intermetallics
• Lattice defects