Influence of microstructure and strain rate on adiabatic shearing behavior in Ti-6Al-4V alloys

Adiabatic shearing behavior of Ti-6Al-4V alloys with bimodal and lamellar microstructures is investigated at strain rates ranging from 10³ s^-1 to 10⁴ s^-1 by Spilt Hopkinson Pressure Bar and Taylor impact. The characteristic of fracture is closely related with the behavior of adiabatic shear band in Ti-6Al-4V alloys. In bimodal microstructure at strain rate of 10³ s^-1, the adiabatic shear bands are regularly spaced and orientated along the maximum shear stress plane. In case of the lamellar microstructure, when the strain rates increase from 4000 s^-1 to 6000 s^-1, the adiabatic shear bands go through the transition from self-organization to branching off and interconnecting into a net-like structure. At strain rate of 10⁴ s^-1 by Taylor impact, the regularly spaced adiabatic shearing cracks cause that the fracture surface makes an angle of 45° with the impacted end of the projectile in bimodal microstructure. The net-like adiabatic shearing cracks in lamellar microstructure result in the fragmentation of the projectile head, the angle is about 0°.