A compressive split-Hopkinson pressure bar and transmission electron microscope (TEM) are used to investigate the mechanical behavior and microstructural evolution of biomedical Ti alloy deformed at strain rates ranging from 8 · 10 2 s -1 to 8 · 10 3 s -1 at temperatures between 25°C and 900°C. In general, the results indicate that the mechanical behavior and microstructural evolution of the alloy are highly sensitive to both the strain rate and the temperature conditions. The flow-stress curves are found to include both a work-hardening region and a work-softening region. The strain-rate-sensitivity parameter, b, increases with increasing strain and strain rate but decreases with increasing temperature. The activation energy varies inversely with the flow stress and has a low value at high deformation strain rates and low temperatures. Microstructural observations reveal that the strengthening effect evident in the deformed alloy is a result primarily of dislocations and the formation of a phase. The dislocation density increases with increasing strain rate but decreases with increasing temperature. Additionally, the square root of the dislocation density varies linearly with the flow stress. Correlating the mechanical properties of the biomedical Ti alloy with the TEM observations, it is inferred that the precipitation of a phase dominates the fracture strain. Transmission electron microscope observations reveal that the amount of a phase increases with increasing temperature below the b-transus temperature. The maximum amount of a phase is formed at a temperature of 700°C and results in the minimum fracture strain observed under the current loading conditions.

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 900u 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.

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