High strain rate deformation of Ti-15Mo-5Zr-3Al alloy over wide temperature range

This study employs a split Hopkinson pressure bar to investigate the deformation behaviour of Ti-15Mo-5Zr-3Al alloy under strain rates of 8 × 10² to 8 × 10³ s^-1 at temperatures ranging from 25 to 900°C. The mechanical properties and fracture features of the alloy are found to be significantly dependent on both the strain rate and the temperature. The flow stress increases with increasing strain rate, but decreases with increasing temperature. For a constant temperature, the work hardening rate, maximum stress, strain at maximum stress and fracture strain all increase with increasing strain rate. For a given strain rate, the mechanical properties of Ti-15Mo-5Zr-3Al alloy exhibit their lowest values at a temperature of ∼700°C. As the strain rate increases, the strain rate sensitivity increases, but the activation volume decreases. However, as the temperature increases, the strain rate sensitivity decreases and the activation volume increases. For the current strain rate and temperature conditions, the activation energy decreases with increasing flow stress. Finally, optical microscopy (OM) and scanning electron microscopy (SEM) observations reveal that the alloy specimens fracture primarily as the result of the formation of adiabatic shear bands. The presence of dimples on the fracture surfaces is indicative of a ductile failure mode. The density of the dimples reflects the toughness of the alloy specimen and is found to vary directly as a function of the strain rate and the temperature.