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

Abstract

The microstructure and phase composition of Al/Ti/Al interfaces with respect to their localization were investigated. An aluminum-flyer plate exhibited finer grains located close to the upper interface than those present within the aluminum-base plate. The same tendency, but with a higher number of twins, was observed for titanium. Good quality bonding with a wavy shape and four intermetallic phases, namely, TiAl 3 , TiAl, TiAl 2 , and Ti 3 Al, was only obtained at the interface closer to the explosive material. The other interface was planar with three intermetallic compounds, excluding the metastable TiAl 2 phase. As a result of a 100-hour annealing at 903 K (630°C), an Al/TiAl 3 /Ti/TiAl 3 /Al sandwich was manufactured, formed with single crystalline Al layers. A substantial difference between the intermetallic layer thicknesses was measured, with 235.3 and 167.4 lm obtained for the layers corresponding to the upper and lower interfaces, respectively. An examination by transmission electron microscopy of a thin foil taken from the interface area after a 1-hour annealing at 825 K (552°C) showed a mixture of randomly located TiAl 3 grains within the aluminum. Finally, the hardness results were correlated with the microstructural changes across the samples.

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

“…Chemical composition of the intermetallic phase in each sample was determined by EDS point analysis. These results were also confirmed by the synchrotron measurements, which are presented elsewhere [1].…”

“…Our previous study showed that already after EXW process the significant difference of two interfaces may be observed [1,2]. The upper interface, located closer to the detonation material and therefore exposed to greater plastic deformation, possessed a wavy morphology and is composed of fine grains of light contrast in dark matrix.…”

“…However, the electron backscatter diffraction technique applied in [1] showed that at lower interface also the very fine-grained zone was created, which can be missed during an ordinary BSE-SEM examination. Moreover, the synchrotron radiation experiment revealed the presence of Ti 3 -Al, TiAl and TiAl 3 at both interfaces [1]. Additionally, in the upper interface the metastable TiAl 2 phase was also observed.…”

“…Depending on the experimental conditions a wavy or planar interface can be formed. Previous observations (SEM, TEM) of such interfaces demonstrated that they are composed of very fine grained Al with locally present intermetallic phases such as TiAl 3 , TiAl, Ti 3 Al and metastable TiAl 2 , which are present in a larger amount inside the nodes areas but also between them [1,2]. Further annealing of such joined materials is associated with production of metallic-intermetallic composite materials, which may found potential application as ballistic armors.…”

“…Due to this the joined materials undergo severe plastic deformation, which changes with respect to the localization of detonation materials [1,2]. Depending on the experimental conditions a wavy or planar interface can be formed.…”