Synergistic effect of twin consumption within lamellae and slip system activation at grain boundary on the formation of nano-spherical B2 phase

Abstract

In this study, the spheroidization behavior of the B2 phase in TiAl alloys under isothermal compression is revealed for the first time, reducing the cut apart trend on matrix. Results show that the deformation stored energy under the 1050 °C–40 %–0.01s−1 condition is insufficient so that most B2 phase bends and twists with the γ lamellae rather than being spheroidized. Under the 1000 °C–80 %–0.01s−1 condition, reduced temperature and increased strain further promote B2 phase spheroidization. The B2 phase nucleates and becomes spheroidized by twin boundary consumption within the γ lamellae. At the γ recrystallized grain boundary, the B2 phase grows into a spherical crown shape due to favorable slip tendency activation, multiple dislocation shear, and microslip bands coordination. This work offers a significant approach to improving the hot workability of TiAl alloys.