Hot Deformation Behavior of New High Strength and Toughness Titanium Alloy

The hot deformation behaviors of a new type high strength and toughness TB17 titanium alloy were investigated on the thermo- mechanical simulator (Gleeble3800). The experiment was conducted in the temperatures range from 775 °C to 905 °C and strain rate range from 0.001 s-1 to 10 s-1. The softening mechanism of flow stress and microstructure evolution were investigated during hot deformation process and the Arrhenius type constitutive equation was established as well. The results show that the stress of TB17 titanium alloy varies with sensitivity of the strain rate at different deformation temperatures. During deforming at α+β field, the peak stress is sensitive to low strain rates, while when deforming at β field, the peak stress is sensitive to high strain rates. The strain rate has a major impact on the microstructure of TB17 titanium alloy. The dynamic recovery mechanisms plays an dominant role as the strain rate exceeds 0.1 s-1. Dynamic recrystallization plays a significant role while the strain rate is in the range of 0.001~0.1 s-1. Recrystallization processing can be promoted with the decreasing of strain rate. The microstructure of equiaxed grains with a size of 25 μm is obtained with a strain rate of 0.001 s-1. The temperature also has great influence on the dynamic recrystallization. Deformation at α+β field leads to primary α phase recrystallization, while at β field leads to the β grain recrystallization. The activation energy for hot deformation below and above the temperature of phase transformation point is 538.4 and 397.4 kJ/mol, respectively. The softening mechanism of hot deformation between 775 and 905 °C transformation point is grain boundary glide. © 2018, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.