Response of titanium alloys to high strain rate deformation

The stress-strain response of samples of Ti64 and Ti550 at strain rates from 10⁻¹ s⁻¹ to 10³ s⁻¹ and samples of Ti811 and Ti153 at a strain rate of 10³ s⁻¹ have been assessed. It has been found that the influence of the imposed strain rate on the stress-strain response of Ti64 and Ti550 alloys is very similar – in both alloys the yield stress increases with increase of strain rate and the energy absorbed to fracture increases. At high strain rates localised deformation occurs in the form of shear bands in Ti64 and Ti550 but no shear banding was seen in Ti811 and Ti153. The fracture surfaces of Ti64 and of Ti550 show an increased tendency to brittle failure and an increase in necking with increase of strain rate. The influence of alloy microstructure and composition on the response to changes in imposed strain rate are discussed in terms of adiabatic heating and the factors controlling the flow stress in these alloys.