Microstructural evolution in the bonding zones of co-extruded aluminium/titanium

In the present study, the interfacial microstructure of dissimilar Al/Ti joints formed by a co-extrusion process has been investigated. The material combinations used for the experiments were commercially pure aluminium and titanium, respectively, in the alloys EN AW-6082 and TiAl6V4. X-ray diffraction, energy-dispersive X-ray spectroscopy, electron microscopy and electron backscatter diffraction revealed titanium aluminide formation in the interface, the development of deformation bands in the sleeve material, and the occurrence of grain size refinement and twinning in the core material. The results are discussed with respect to the concept of a hard core-soft sleeve co-extrusion comprising plastic deformation to promote solid-state diffusion. The study shows the phase distribution and the microstructural evolution in the bonding zone with the aim to improve the quality of the bonding by adequately adjusting the process parameters.