Microstructure Changes and Phase Growth Occurring at the Interface of the Al/Ti Explosively Welded and Annealed Joints

Abstract

The manuscript presents a close examination of the titanium and aluminum platters manufactured by explosive welding method. In particular, the microstructure changes of the Al/Ti wavy shape interface after annealing at 773 and 903 K were studied. Three stable TiAl 3 , TiAl, and Ti 3 Al and a metastable TiAl 2 intermetallic phases have been formed in the state directly after explosive welding. The orientation map and TEM images obtained after explosive welding process showed very fine grains of aluminum mixed with intermetallics in the interface region between the peninsulas or islands. After annealing for 100 h the TiAl 3 continuous layer was obtained; however, the layer achieved at 903 K was much wider than that obtained at 773 K. An examination of the growth kinetics at 903 K revealed that incubation time was less than 5 min. After this period, the growth was solely governed by chemical reaction.

Growth kinetics of TiAl 3 phase in annealed Al/Ti/Al explosively welded clads

“…3 presents the growth kinetics of the TiAl 3 phase described previously in the literature for 903 K [3][4][5][6] or slightly higher 913 K [7]. All these data (including ours for the one interface case Al/Ti [3]) reveal different mechanisms of growth and velocities. As it was previously stated, this all might hold true due to the fact of different explosive welding conditions and the resulting refinement of the microstructure close to the interface area.…”

“…Further annealing of such joined materials is associated with production of metallic-intermetallic composite materials, which may found potential application as ballistic armors. The growth kinetics of TiAl 3 at 903 K was the subject of several studies, where the EXW process was applied [3][4][5][6][7]. These works bring different data, which is most probably associated with the influence of the EXW parameters such as detonation velocity or thickness of the plates.…”

Microstructural and Phase Composition Differences Across the Interfaces in Al/Ti/Al Explosively Welded Clads

“…The phase analysis completed by a selected area diffraction pattern (SADP) showed two stable phases, namely, Ti 3 Al and TiAl, and one metastable phase, TiAl 2 , while the TiAl 3 phase was not detected. The TiAl 2 intermetallic phase was also detected in our previous work concerning two-layered Ti/Al samples, [30,31] although in other works on the Ti/ Al system, it was not observed. [22,24,[32][33][34] Subsequently, the investigated thin foil was annealed for 1 hour at 825 K (552°C) in a calorimeter in order to observe the influence of postheating on structural heterogeneity and phase changes.…”

“…However, in contrast to our previous studies, they did not form peninsula-or island like structures. [30,31] According to the Ti-Al phase equilibrium diagram, [49] three stable phases, namely, Ti 3 Al, TiAl, and TiAl 3 , or a metastable TiAl 2 phase, can be formed. The chemical composition analysis carried out in intensely mixed node regions by means of SEM/EDS revealed the presence of TiAl 2 , TiAl, and TiAl 3 phases (examples in the tables in Figure 3).…”

“…Alternatively, further annealing causes the growth of a thermodynamically favored TiAl 3 intermetallic phase. [23,25,[30][31][32][33] The manufacturing of EXW clads requires a number of parameters to be controlled, such as the collision angle, impact velocity, detonation pressure, and geometry, with respect to the type of bonded materials. [28,[34][35][36][37][38][39] However, the problem becomes even more complicated when more than only one interface is obtained.…”