Effect of microstructure on mechanical properties of titanium-steel explosive welding interface

Explosive welding, as a well-known composite processing technology, can be used to weld two or more similar and dissimilar materials. Generally, periodic wavy interfaces are formed in the bonding zone during explosive welding process. The bonding strengths of the welding interfaces are largely influenced by the microstructure of the welding interface. In this paper, the effects of microstructure on mechanical properties of titanium-steel explosive welding interface were presented. The bonding interface with different microstructure at different locations of the titanium-steel welding interface can be characterized as three distinct zones due to different stages of detonation wave propagation including the detonation growth zone near the initiation point, steady detonation zone and reflection-affected zone near the far-end boundary. The microstructure of interfaces was investigated by optical microscopy, scanning electron microscopy, energy dispersive spectrometer. It was found that a nearly straight interface with a small wavy interface was created in the detonation growth zone near the initiation point, and an irregularly wavy interface was formed in the reflection-affected zone near the far-end boundary. While a periodic wavy interface with various defects (e. g. microcracks, voids and intermetallic compounds etc.) was formed in the steady detonation zone. A small-size H-shaped specimen was used to evaluate the tensile properties of interfaces with the bonding interface perpendicular or parallel to the tensile loading direction. The results indicated that the amplitude and wavelength of wavy interfaces showed a tendency of increasing, plateauing and decreasing, corresponding to the detonation growth zone, steady detonation zone and reflection-affected zone, respectively. The mechanical properties of the bonding interface along the detonation direction also displayed a similar tendency. The periodic wavy interface in the steady detonation zone exhibited the highest strength. Notably, the defects, such as microcracks, void and intermetallic compounds in the vortex area had significant effects on the mechanical properties of the bonding interface.