Adiabatic shear behaviors in rolled and annealed pure titanium subjected to dynamic impact loading

The hat-shaped samples cut from rolled and annealed titanium plates were prepared to explore the adiabatic shear behaviors subjected to high-strain-rate deformation operated via Split Hopkinson Pressure Bar. The dynamic shear response calculation reveals that dynamic deformation processes of both state samples can be divided in similar three stages but rolled sample shows a higher susceptibility of adiabatic shear localization compared with the annealed one. Optical microscopy and electronic backscatter diffraction technique (EBSD) were used to systematically analyze the microstructure and texture characteristics. The results show that adiabatic shear bands form in both state samples and rotational dynamic recrystallization (RDRX) occurs within shear area and results in the formation of ultrafine equiaxed grains. Furthermore, ultrafine equiaxed grains within adiabatic shear bands have the same texture feature that <11-20> direction and {10-10} plane parallel to macro local shear direction and shear plane respectively. In the deformation region around the shear band, {10-12} <-1011> tensile and {11-22} <11-2-3> compressive two types twins are observed in both state samples and {10-12} <-1011> tensile twins are more frequently observed in rolled sample. In the rolled sample, {10-12} <-1011> tensile twins are more likely to happen in the hat-brim side than the hat-body side due to the difference of stress state in two sides.