Constitutive model and optimal processing parameters of TC17 alloy with a transformed microstructure via kinetic analysis and processing maps

The kinetic and flow stability analysis of TC17 alloy with a transformed microstructure in the hot deformation of α+β region were carried out. The flow behavior in the hot deformation of TC17 alloy was sensitive to the strain, strain rate and deformation temperature. The work hardening effect dominated the flow in the early stage of deformation, and the globularization, dynamic recrystallization (DRX) occurred in the following deformation, in which the apparent activation energy for deformation decreased with the increasing of strain. A strain compensated constitutive model for hot deformation of TC17 alloy was established. The peak efficiency of power dissipation at the strains of 0.3 and 0.5 occurred at 0.01 s⁻¹ and 1143 K due to α to β transformation and DRX of β phase. However, the peak efficiency of power dissipation at a strain of 0.7 occurred at 0.1 s⁻¹ and 1123 K due to the globularization of α lamellae and DRX of β phase. The flow instability analysis suggested that the safe processing window should not exceed 0.32 s⁻¹. The processing maps of TC17 alloy at different strains were constructed. According to the processing maps and microstructure observation, the optimal processing parameters for globularization of TC17 alloy with a transformed microstructure were at the temperatures ranging from 1043 K to 1123 K and strain rates ranging from 0.01 s⁻¹ to 0.1 s⁻¹.