Anisotropy in microstructure and shear properties of TA2/Q235 explosive welding interfaces

Explosive welding interface commonly show wavy shapes, makes microstructure anisotropic. The effects of microstructure and different loading directions on shear properties of bonding interfaces at dynamic loading conditions are still unclear. In this work, characteristics on transverse and longitudinal sections of TA2/Q235 welding interface was characterized by optical microscopy. It was found that the transverse sections of bonding interface showed wavy shapes with wavelength and amplitude of 1200 μm and 400 μm. The longitudinal sections of bonding interfaces were composed of wavy interface, dislocation shaped interface and stacking fault shaped interface, which was explained by non-equilibrium theory. A small-size S-shaped specimens was processed to investigate shear properties of bonding interface varied with orientation angles (0°, 45°and 90°) at both quasi-static (0.001 s⁻¹) and dynamic (5000∼7000 s⁻¹) loadings. Meanwhile, fracture mechanism of interfaces was analyzed by scanning electron microscopy coupled with energy dispersive spectrometer. The results indicated that the maximum shear strength of joining interfaces (380 MPa–410 MPa under quasi-static loading, and 450 MPa–600 MPa under dynamic loading) was obtained along 90° orientation angle. Fluctuation of explosive detonation pressure was the fundamental cause of the interface inhomogeneity, and strength of joining interfaces increases with increasing strain rates, indicating positive strain rate sensitivity. Fracture mainly occurred in bonding interfaces near TA2 side at quasi-state loading, and failure occurred in interface waves at dynamic loading because of TA2 showed more obvious strain rate sensitivity than Q235. Fracture morphology indicated the ductile-brittle mixed fracture occurred in both quasi-static and dynamic tests.