Damage Behavior of Craters and Microstructure Evolution in Ti-6Al-4V Alloy by Twice Penetration

The target of Ti-6Al-4V alloy was impacted vertically by an armored steel plane bullet. The damage behavior of craters and microstructure evolution in twice penetration under the same ballistics condition were analyzed. The results show that the adiabatic shear bands formed in twice penetration come into being at 45 degrees direction along with stress. The shear bands occurring in the first penetration are petty with winding and warping, and expand from 45 degrees to 30 degrees along with the shallow surface. Nevertheless, the shear bands occurring in the second penetration are longer with a large number of apertures and cavities, and expand from 45 degrees to parallel with the shocking-loading direction. Results indicate that the heavier shear damage of the second impact than that of the first impact is owing to the formation of the shear bands in the first penetration, which could cause the increasing of strength of target material and the heterogeneity of the residual stress as well as the residual stress, the stress superposition, local strain hardening and strain rate hardening caused by the second penetration.