The flow behavior and processing maps during the isothermal compression of Ti17 alloy

Isothermal compression tests of Ti17 alloy were conducted on a Gleeble-1500 simulator at the deformation temperatures ranging from 770°C to 870°C, strain rates ranging from 0.01s^-1 to 5.0s^-1, and strains ranging from 0.5 to 0.9. The effect of processing parameters on the flow stress and strain rate sensitivity (m) was investigated to characterize the deformation behavior of Ti17 alloy. The processing maps based on dynamic material modeling (DMM) were developed at different strains to represent the deformation mechanisms during the isothermal compression of Ti17 alloy. Moreover, the microstructure evolution was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to verify the deformation mechanisms. The results show that the maximum m value of 0.42 occurs at 770°C/0.01s^-1. High ductility value of about 180% in this domain confirms the superplastic deformation behavior of the material. The unstable domains in instability map increase at the strains ranging from 0.3 to 0.7, which implies that the processing window of Ti17 alloy becomes narrow with increasing strain. The peak efficiency of power dissipation occurs at 770°C/0.01s^-1 and the strains range from 0.3 to 0.6, corresponding to the optimal deformation condition of Ti17 alloy. By the analysis of microstructure evolution of Ti17 alloy, it is confirmed that dynamic recrystallization occurs at 790°C/0.01s^-1 and dynamic recovery is a dominant softening mechanism at higher strain rates (≥1.0s^-1).