Abstract:To control the tri-modal microstructure and performance, a prediction model of tri-modal microstructure in the isothermal local loading forming of titanium alloy was developed. The staged isothermal local loading experiment on TA15 alloy indicates that there exist four important microstructure evolution phenomena in the development of tri-modal microstructure, i.e., the generation of lamellar α, content variation of equiaxed α, spatial orientation change of lamellar α and globularization of lamellar α. Considering the laws of these microstructure phenomena, the microstructure model was established to correlate the parameters of tri-modal microstructure and processing conditions. Then, the developed microstructure model was integrated with finite element (FE) model to predict the tri-modal microstructure in the isothermal local loading forming. Its reliability and accuracy were verified by the microstructure observation at different locations of sample. Good agreements between the predicted and experimental results suggest that the developed microstructure model and its combination with FE model are effective in the prediction of tri-modal microstructure in the isothermal local loading forming of TA15 alloy.

Key words: titanium alloy; isothermal local loading forming; complex thermomechanical processing history; tri-modal microstructure modelling