High Temperature Deformation Behavior of Near-β Titanium Alloy Ti-3Al-6Cr-5V-5Mo at α plus β and β Phase Fields

Most near-beta titanium alloy structural components should be plastically deformed at high temperatures. Inappropriate high-temperature deformed processes can lead to macro-defects and abnormally coarse grains. Ti-3Al-6Cr-5V-5Mo alloy is a near-beta titanium alloy with the potential application. The available information on the high-temperature deformation behavior of the alloy is limited. To provide guidance for the actual hot working of the alloy, the flow stress behavior and processing map at alpha + beta phase field and beta phase field were studied, respectively. Based on the experimental data obtained from hot compressing simulations at the range of temperature from 700 degrees C to 820 degrees C and at the range of strain rate from 0.001 s(-1) to 10 s(-1), the constitutive models, as well as the processing map, were obtained. For the constitutive models at the alpha + beta phase field and beta phase field, the correlated coefficients between actual stress and predicted stress are 0.986 and 0.983, and the predictive mean relative errors are 2.7% and 4.1%. The verification of constitutive models demonstrates that constitutive equations can predict flow stress well. An instability region in the range of temperature from 700 degrees C to 780 degrees C and the range of strain rates from 0.08 s(-1) to 10 s(-1), as well as a suitable region for thermomechanical processing in the range of temperature from 790 degrees C to 800 degrees C and the range of strain rates from 0.001 s(-1) to 0.007 s(-1), was predicted by the processing map and confirmed by the hot-deformed microstructural verification. After the deformation at 790 degrees C/0.001 s(-1), the maximum number of dynamic recrystallization grains and the minimum average grain size of 17 mu m were obtained, which is consistent with the high power-dissipation coefficient region predicted by the processing map.