Abstract
Load-displacement curves of a solution-treated β titanium alloy were investigated in the temperature range between 77 and 355K at the crosshead speed from 0.05 to 50mm/min (initial strain rate from 3.3×10-5 to 3.3×10-2s-1).
At higher temperature or lower crosshead speed, the alloy work-hardens gradually as it deforms and reaches the plastic instability after showing some uniform elongation. On the other hand, at lower temperature or higher crosshead speed, the alloy shows the plastic instability at the very initial stage of plastic deformation.
The above-mentioned results were discussed, based on the equation of plastic instability, dσ/dε=σ.
The flow stress increases remarkably with a decrease in test temperature or with an increase in strain rate. However, the work-hardening rate little depends on strain and strain rate, and increases proportionally to the Young's modulus with a decrease in test temperature.
Thus, it is concluded that the plastic instability occurrs at the earlier stage of deformation as the temperature lowers or the strain rate increases.
