Microstructure characteristics and strain rate sensitivity of a biomedical Ti–25Nb–3Zr–3Mo–2Sn titanium alloy during thermomechanical processing

Microstructure characteristics and strain rate sensitivity of Ti–25Nb–3Zr–3Mo–2Sn alloy were studied by compression deformation at 850 °C and strain rate of 0.001–50 s−1, to give a basic understanding for the alloy being able to obtain a reasonable microstructure by thermomechanical processing. The results show that both microstructure evolution and flow behavior are sensitive to strain rate. At the lower strain rates of 0.001–0.1 s−1, dynamic recovery leads to abundant sub-grains. At the higher strain rates of 1–50 s−1, dynamic recrystallization (DRX) is activated in small extent, resulting in the localized grain refinement and a decreased strain rate sensitivity (m). Two typical orientation accumulation patterns, i.e., continuous accumulation and multi-peak orientation, are prone to occur at the lower and higher strain rates, respectively. It is considered that the activated DRX is associated with the strain concentration and deformation heating. The former promotes the boundary bugling and migration as well as misorientation accumulations, while the latter provides an energy potential needed for grain nucleation, and accelerates the rearrangement of the mobile dislocations into low-energy configurations.