Hot Deformation Behavior and Microstructural Evolution of a Near-α Ti-5Al-1Sn-1 V-1Zr-0.8Mo Titanium Alloy during Isothermal Compression

Herein, the hot deformation behavior of a near-alpha Ti-5Al-1Sn-1 V-1Zr-0.8Mo (Ti-5111) titanium alloy was studied at 870-1050 degrees C during isothermal compression tests at a strain rate of 0.01-10.0 s(-1). The microstructural evolution mechanism in the titanium alloy was systematically analyzed. Results show that the flow stress values rapidly increase to the peak value and gradually decrease as the strain variable increases. Further, the peak stress declines with the increasing deformation temperature. The apparent activation energy values of (alpha + beta) and beta regions are 438 and 206 kJ mol(-1), respectively. The variation of flow stress against temperature and strain rate is established using the constitutive equation. The safe processing zones are 890-960 degrees C and 960-1010 degrees C at strain rates of 0.01-0.3 s(-1) and 0.1-2 s(-1), respectively, as determined using the hot processing diagram. The maximum energy dissipation efficiency is 0.59 at 0.01 s(-1) and 930 degrees C, which is the optimum processing technique. The flow instability for the Ti-5111 alloy will occur at a high strain rate when shear bands and microscopic cracks appear in the deformed microstructures. Therefore, processing Ti-5111 alloy in unstable zones of the hot processing diagram should be avoided.