Explosively welded multilayer Ti-Al composites: Structure and transformation during heat treatment

In this study, forty-layered Ti-Al composites were fabricated in a single-shot explosive welding process. The structure of the composites was thoroughly investigated using scanning and transmission electron microscopy. Particular attention was paid to the structure of the mixing zones (vortexes) arising at the interfaces during explosive welding. The complicated process of mixing and rapid solidification of these zones led to formation of different stable and metastable structures. The vitrification of vortexes, formation of “disordered” Ti3Al and ordered solid solution of Al in hexagonal-Ti and Ti in FCC-Al were observed and discussed with respect to the conditions of solidification. Subsequent heat treatment was carried out at 640 °C under atmospheric and at 3 MPa pressure. For comparison, there were produced reference samples by reaction sintering at the same conditions as for the heat treatment. The heat treatment and reaction sintering promoted the formation of stable Al3Ti phase between Ti and Al. It was found that preliminary explosive welding accelerated the formation of Al3Ti layer and made heat treatment duration four times shorter. The application of pressure was found to play an important role at the final stage of heat treatment after explosion welding to avoid formation of defects between the plates. Keywords: Explosive welding, Multilayer, Titanium, Aluminum, Intermetallic, Composite