Flow softening and microstructural evolution of TC11 titanium alloy during hot deformation

Hot compression tests on samples of the TC11 (Ti-6.5Al-3.5Mo-1.5Zr-0.3Si) titanium alloy have been done within the temperatures of 750-950 degrees C and strain rate ranges of 0.1-10s(-1) to 40-60% height reduction. The experimental results show that the flow stress behavior can be described by an exponential law for the deformation conditions. The hot deformation activation energy (Q) derived from the experimental data is 538 kJ mol(-1) with a strain rate sensitivity exponent (m) of 0.107. Optical microstructure evidence shows that dynamic recrystallization (DRX) takes place during the deformation process. Moreover, only a DRX grains are founded in the titanium alloys. The influences of hot working parameters on the flow stress behavior and microstructural features of TC11 alloy, especially on the type of phase present, the morphologies of the a phase, grain size and DRX are analyzed. The optimum parameters for hot working of TC11 alloy are developed. (C) 2008 Elsevier B.V. All rights reserved.