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 degrees C with 20 degrees 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 ln epsilon(over dot) - ln[sinh(alpha sigma)] plot is lower than ln epsilon(over dot) - sigma 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 alpha lath. As a thermal diffusion process, the strain rate plays a remarkable effect on the globularization. The fraction of globularized alpha lath increased with the increase of the strain rate. Meanwhile, the globularization is sensitive to the orientation. At lower strain, only local favorable orientation alpha lath occurred globularization. With the increase of the strain, more alpha lath became kinking and globularization. The optimum deformation parameter for the globularization is in the temperature rang 990-1010 degrees C, strain rate 0.01 s(-1) and height reduction of 60%. (C) 2019 Elsevier B.V. All rights reserved.