Structural properties of Ti/Al clads manufactured by explosive welding and annealing

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

“…There are other metastable phases that have been found in the literature, such as Ti 3 Al 5 and h-TiAl 2 , as shown by Lazurenko et al [25] and Palm et al [52] ; however, these were not observed in the current study. As presented in our previous work, [30] a small intensity of the analyzed reflections indicates a minor volume fraction of intermetallics in the sample. Additionally, intermetallic crystallites were not randomly oriented and some degree of texture was present.…”

“…[30] In the current work, both interfaces were of good quality without pores or hollows, in contrast to the interface in two-layered Ti/Al shown in Figure 5(e) in Reference 31. Both types of clads were manufactured with the use of a detonation velocity in the range of 1900 to 1950 m/ s. This confirms that the other initial manufacturing conditions, such as collision angle or detonation pressure, also play a crucial role in determining strongly not only the microstructure of the obtained platter but also the growth velocity of the intermetallic phase at the interface during heat treatment.…”

“…However, the SEM/ EDS measurements have to be supported by other analytical techniques, since, as reported in the literature, an accelerating voltage of 12 kV induces an interaction volume of about 1.2 lm 3 , which implies that signals coming from different phases might be included. [30] Comparison of the upper and lower interfaces confirmed that dissimilar scenarios occurred on each interface, and as a result, different morphologies, microstructures, and chemical compositions were obtained. As mentioned previously, the upper interface, because of its closer proximity to the explosive material, was exposed to a greater impact force and, as a consequence, apart from the waviness, was characterized by a significantly more complex microstructure with swirled intermetallics, as well as intermediate phases scattered within the Al clad.…”

“…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.…”