Research on the dynamic globularization kinetics of Ti-17 titanium alloy with initial lamellar microstructure during hot deformation

It is quite significant to quantitatively research the dynamic globularization kinetics of Ti-17 titanium alloy with lamellar microstructures because such investigation is one of the critical issues in terms of achieving optimum forging processing and desired perform shape. In the present work, isothermal compression tests of the Ti-17 titanium alloy has been conducted on the Gleeb-1500 simulator in the deformation temperatures range of 780-860°C and strain rates range of 0.001-10s^-1 In order to obtain the globularized volume fraction, micrographic observations were carried out using software of quantitative image analysis (Image-pro Plus 5.0). It was found that the dynamic globularization kinetics and the kinetics rate were fairly sensitive to the various deformation conditions. The fraction of dynamic globularization approximately increased with strain in an Avrami type sigmoid way, as well as increased with increasing temperature and decreasing strain rate. The strains for initiation and completion of dynamic globularization were predicted through the fitting curves of dynamic globularization kinetics at different processing conditions, around 0.04-0.47 and 1.34-5.36 respectively. In addition, the critical strains for initiation and completion of dynamic globularization are analyzed. The process of dynamic globularization is obviously restricted by the rate of migration of intraphase boundary.