The dynamic softening identification and constitutive equation establishment of Ti–6.5Al–2Sn–4Zr–4Mo–1W–0.2Si alloy with initial lamellar microstructure

Abstract The high-temperature deformation behavior of Ti–6.5Al–2Sn–4Zr–4Mo–1W–0.2Si alloy with initial lamellar microstructure was investigated through performing hot compression experiments at temperatures of 940–1,030°C and strain rates of 0.001–10 s−1 on the Gleeble-3500 simulator. Three kinds of typical flow curves corresponding to different strain rates were distinguished. The deformation activation energy and Zener–Hollomon parameter were obtained through kinetic analysis. By comparing saturated dislocation density with the critical density for dynamic recrystallization, dynamic softening behaviors were identified and verified by the Poliak–Jonas criterion. Furthermore, a piecewise physical-based constitutive model incorporating dynamic softening behaviors was constructed. Finally, microstructures deformed under different deformation conditions were analyzed to further verify the softening behaviors determined by identification criterions.