Deformation behavior and microstructure evolution during hot working of Ti60 alloy with lamellar starting microstructure

The hot deformation behavior and microstructure evolution of Ti60 alloy with lamellar starting microstructure were investigated through hot compression test in the temperature range 970–1030 °C with 20 °C intervals, strain rate range 0.01–10 s⁻¹ and height reductions of 40%, 60% and 80%. On the basis of the flow stress obtained as a function of the strain rate and deformation temperature, the constitutive equation was established. It was found that the hyperbolic sine law equation is more applicable than the exponential law equation since the relative standard deviation of lnε˙−ln[sinh(ασ)] plot is lower than lnε˙−σ plot, and the hot deformation activation energy is calculated to be 839 kJ/mol. The results also showed that the deformation mechanism mainly involves the globularization of the α lath. As a thermal diffusion process, the strain rate plays a remarkable effect on the globularization. The fraction of globularized α lath increased with the increase of the strain rate. Meanwhile, the globularization is sensitive to the orientation. At lower strain, only local favorable orientation α lath occurred globularization. With the increase of the strain, more α lath became kinking and globularization. The optimum deformation parameter for the globularization is in the temperature rang 990–1010 °C, strain rate 0.01 s⁻¹ and height reduction of 60%.