Impact Deformation and Dislocation Substructure of Ti-6al-7nb Biomedical Alloy
The high temperature deformation and dislocation substructure of Ti-6Al-7Nb biomedical alloy are investigated
under high strain rate loading conditions using a split-Hopkinson pressure bar. Impact tests are performed at strain rates
ranging from 1x103s-1 to 3x103s-1 and temperatures of 300℃and 700℃, respectively. The experimental results show that the
flow stress, work hardening coefficient and strain rate sensitivity all increase with increasing strain rate, but decrease with
increasing temperature. Transmission electron microscopy observations reveal that the dislocation density increases with
increasing strain rate, but decreases with increasing temperature. A pronounced thermal softening effect is observed in the
specimens deformed at 700℃ due to the rapid annihilation of the dislocations. However, a work hardening effect occurs at
higher strain rates and lower temperatures due to an enhanced degree of dislocation multiplication and tangling. Finally, a
linear relationship is observed between the square root of the dislocation density and the flow stress.
Keywords - Split-Hopkinson Pressure Bar, Ti-6Al-7Nb Biomedical Alloy, Impact, Strain Rate, Dislocation.