Hot deformation behavior of new type of near β type Ti-5.5Mo-6V-7Cr-4Al-2Sn-1Fe alloy

The isothermal constant strain rate compression tests of Ti-5.5Mo-6V-7Cr-4Al-2Sn-1Fe alloy were conducted by Gleeble-3800 simulator. The hot deformation temperature range is from 655℃ to 855℃ and the strain rate range is from 0.001s-1 to 10s-1 and the maximum true strain is 0.8. A high temperature flow stress model was built with activation energy of 255kJ/mol according to the experimental results for the alloy and the processing map of alloy was constructed according to DMM model. The metallographic analysis of alloy shows that the alloy exhibits domain of flow localization and adiabatic shear bands and low power dissipation efficiency in the high strain rate(1-10s-1). The alloy undergoes dynamic recovery in the temperature region of 655-755℃ and the strain rate below 0.01s-1. The dynamic recrystallization takes place at the strain rate below 0.01s-1 and in the temperature region of 755-855℃, the original deformed grains and recrystallized grains gradually grow with the increase of temperature. When the temperature is 755-770℃ and the strain rate is 0.001-0.003s-1, the alloy's power dissipation efficiency reaches the maximum and the recrystallized grain is uniform and fine. These regions can be considered as the optimal parameter range of isothermal compression for the alloy