Phenomenological Constitutive Model and Physical Constitutive Model of Hot Deformed Dual-Phase Ti-5Al-4Sn-2Zr-5Mo Alloy

Hot compression experiments on dual-phase titanium alloy Ti-5Al-4Sn-2Zr-5Mo at 880–1000°C, 0.001–10 s⁻¹ and the Arrhenius constitutive model and physical constitutive model were established for the thermal deformation of the alloy. The flow stress prediction shows that the correlation coefficient R values of the Arrhenius constitutive model and the physical constitutive model are 0.9845 and 0.9748, respectively, and the average relative errors AARE are 7.434% and 8.647%, respectively, indicating that the Arrhenius constitutive model has higher prediction accuracy. According to the dynamic material model to map the thermal processing map, the peaks of power dissipation efficiency η appeared at 880°C, 0.001 s⁻¹ and 975–1000°C, 0.001–0.1 s⁻¹, and the instability region was mainly centered at 880–930°C, 0.1–10 s⁻¹ and 980–1000°C, 1–10 s⁻¹. Observations by electron back-scatter diffraction and transmission electron microscopy revealed that the softening behavior at 880–940°C, 0.001 s⁻¹ was discontinuous dynamic recrystallization, and continuous dynamic recrystallization appeared at 940°C, 1 s⁻¹. At 970–1000°C and 0.001 s⁻¹, with the coexistence of two softening mechanisms, dynamic recrystallization and dynamic recovery took place. It is therefore concluded that a thermal processing map has a high degree of accuracy.