Hot deformation behavior and microstructural evolution of powder metallurgical TiAl alloy

The hot deformation behavior of powder metallurgical (PM) TiAl alloys was investigated on Gleeble-3500 thermomechanical simulator, at a temperature range of 1050-1200 A degrees C with an interval of 50 A degrees C and a strain rate range of 0.001-1.000 s(-1). The results show that the flow stress of PM TiAl alloy is sensitive to deformation temperature and strain rate, the peak stress decreases with the increase in deformation temperature and decrease in strain rate, and dynamic recrystallization occurs during the hot compression. The deformation active energy was calculated and the flow stress model during high-temperature deformation was established based on the Arrhenius equations and Zener-Hollomon parameter. The deformed microstructure consists of refined homogeneous gamma and alpha(2)/gamma grains. The fully dynamic recrystallization microstructure can be obtained when deformed at temperature 1150 A degrees C and strain rate 0.001 s(-1). Dynamic recrystallization plays an important role in hot working of PM TiAl alloy, and deformation temperature and strain rate have a strong effect on the recrystallization microstructure. The degree of dynamic recrystallization obviously improves with the increase in temperature. And refinement of recrystallization grains takes place as strain rate increases at a given temperature.