Influence of shock pre-strain on the dynamic mechanical behavior and adiabatic shearing failure of the Ti-6Al-4V alloy with lamellar microstructure

The effects of shock (high-strain-rate) and quasi-static pre-strain on the dynamic mechanical properties and adiabatic shear band (ASB) behavior of Ti-6Al-4V (Ti64) alloy with lamellar microstructure were systematically investigated. The strength improves but the ductility degrades in the all pre-strained Ti64. The strengthening effect is more significantly in the materials pre-strained and reloaded at higher strain rates, due to the more efficient accumulation of defects and the viscous drag effect. The work hardening rate of the shock pre-strained Ti64 shows a complex trend with pre-strain, due to the competition between thermal softening and strain-rate hardening. The failure of the shock pre-strained alloys during dynamic reloading is caused by the cracks that nucleate, grow and propagate along the ASBs. The nucleation and interaction of ASBs in Ti64 are promoted by defects multiplication during the shock wave pulse, resulting in the formation of some special ASB structures such as rings and plugs. Some ASB nodes also generate in the shock pre-strained Ti64 through the more serious localized deformation in the ASB ring formed by the bifurcation, deflection and convergence again of ASBs.