Study on Constitutive Equation for Thermo-compressive Forming of TA1 Titanium Pipe

The thermo-compressive deformation behaviors of the TA1 titanium pipe are investigated with the Gleeble 3500 simulator within a temperature range of 660~780℃ and strain rate range of 0.1~10 s^-1.A linear fitting method is used to determine the material constants and the deformation activation energy to set up the hyperbolic sine function formal constitutive equation.The maximum stresses are predicted by using the Zenner-Hollomon parameter, showing that the predicted values are preferably in compliance with the tested values.The test result demonstrates that the stress-strain curves of the TA1 material show distinctive feature of work hardening, i.e., the rheological stress drops along with the rise of the temperature, and mitigates along with the decrease of the strain rate.It is also revealed that during the thermocompressive deformation process of the TA1 material, the rheological stress is obviously affected by the deformation temperature and the deformation rate, i.e.the rheological stress drops along with the rise of the temperature, and mitigates along with the decrease of the deformation rate.