Solid-state diffusion bonding of gamma-TiAl alloys using Ti/Al thin films as interlayers

Alternating nanometric layers of titanium and aluminium were used as filler material to promote joining between titanium aluminide samples. The improved diffusivity of these nanometric layers is thought to overcome the difficulties in solid-state joining of titanium aluminides without producing chemical discontinuities at the interface. In this study, a thin multilayer (alternating titanium and aluminium layers), 2 μm thick, was deposited by dc-magnetron sputtering onto the two surfaces to be joined. The effects of processing conditions and the thickness of nanometric layers on microstructure and chemical composition variation across the interface have been analyzed. Sound regions can be obtained at temperatures as low as 600 °C but higher temperatures (800–1000 °C) are needed to obtain completely sound joints. During processing, the as-deposited film evolves to a nanocrystalline TiAl layer which may explain why the bond region is slightly harder than the base material.