Softening mechanism and process parameters optimization of Ti-4.2Al-0.005B titanium alloy during hot deformation

The isothermal constant strain rate compression test of Ti-4.2Al-0.005B titanium alloy was carried out by Gleeble-3800 thermal simulator at temperature 850∼1050 °C, strain rate 0.001∼10s−1 and maximum deformation degree 60%. According to the experimental data, the Arrhenius constitutive model was established, the flow stress curve was analyzed, and the processing map based on polarity reciprocity model was established, which was further optimized by Zener-Hollomon parameter processing map and activation energy map. The results show that the flow stress curves respectively show dynamic recovery characteristics and dynamic softening characteristics under different deformation conditions respectively. The softening behavior of the flow stress curves under high strain rate is caused by temperature effect, while the softening behavior at low strain rate is caused by dynamic recrystallization. According to the established Polar Reciprocity Model processing map, the stable region is (870–990 °C/0.01–0.12s−1). Then, the Zener-Hollomon parameter processing map and activation energy processing map were established. Finally, the optimal processing parameters of the alloy are (870–990 °C/0.04–0.12s−1). The main deformation mechanism is dynamic recrystallization. Meanwhile, the rationality of Zener-Hollomon parameter diagram and activation energy diagram is verified. In the actual production process, the choice of technological parameters is provided in order to obtain good microstructure and properties.