Microstructural evolution in the adiabatic shear bands of predeformation TA2

Microstructural evolution of the adiabatic shear bands originated by the deformation of high strain for TA2 has been examined. Tests were performed using a specially designed stepped specimens in a Hopkinson bar. Upon completion of deformation, the region is cooled below half the temperature achieved during adiabatic heating for less than one millisecond. Microstructural characterizations of shear bands were analysed using SEM, TEM and the TEM of high resolving power. No evidence of transition from α-Ti to another phases within the adiabatic shear bands could be found. However, the kinetics of boundary refinement processes were not taken into account in these studies with the distinctive characteristic of recrystallized micro structure. It is shown that there is no phase transformation in the TA2 adiabatic shear bands, which are composed of fine equiaxed grains. The dynamic recrystallization in the TA2 adiabatic shear bands was performed by the mixed mechanism of grain mechanical fragmentation, grain boundary transfer and subgrain roughen, and the recrystallization mechanism of progressive subgrain misorientation.