Characterization of high-temperature deformation behavior and processing map of TB17 titanium alloy

Abstract

Isothermal compression testing of a new high-strength TB17 titanium alloy was investigated on a Gleeble 3800 thermo-mechanical simulator over a temperature range of 775 °C–905 °C and a strain rate range of 0.001 s−1 to 10 s−1 with height reductions of 25%, 50% and 70%. Optical microscopy (OM), transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) were employed to investigate the effect of deformation parameters on the microstructure and the deformation mechanism. The hot deformation behavior of TB17 titanium alloy is characterized by the analysis of the strain-stress curve, the strain rate sensitivity exponent and processing maps. The results show that the flow stress decreases with the increase of the deformation temperature and decrease of the strain rate. The strain rate sensitivity exponent m remains constant in α+β phase field deformation and increases sharply in β phase field. The TB17 titanium alloy has a narrow deformation field and the optimized deformation parameters is found at the temperature of 885 °C and the strain rate of 0.001 s−1 at height reduction of 70%. The microstructure in the α+β phase field deformation is characteristic of refined DRX α phase. While in the β phase, the morphology is characteristic of refined β grains. The increase of strain supported the occurrence of DRX at lower strain rates. The morphology is characterized by flow localization in instability domain.