Influence of the explosively welded composites structure on the diffusion processes occurring during annealing

Currently layered composites with intermetallic interlayers are promising materials for many industries. Materials of this type involve composites consisting of titanium and titanium aluminides layers. One of the methods of such composites fabrication is explosive welding and annealing. In this paper the structure and properties of explosively welded multilayered composites is described. Structural studies were carried out by the methods of optical metallography, scanning and transmission electron microscopy. The properties of local zones of material were estimated by the measuring of a microhardness level. The explosive welding process accompanied by the structural changes of material adjacent to “Al-Ti” interfaces. The structural investigation revealed the formation of several areas: vortex zones, which are characterized by aluminum and titanium mixing, and severely deformed areas. These structural features have the strong influence on the diffusion processes occurring during annealing of composites. The most intensive diffusion was observed in the welded joints where the most significant structural changes occurred. It was identified that Al₃Ti is only one phase which forms during heat treatment of “Ti-Al” composites. The main conditions of “Ti-Al₃Ti” composites fabrication are the correct choice of aluminum and titanium plates thickness and optimal conditions of heat treatment.