Crystal lattice rotations during shear band formation in pure titanium deformed at high strain rate

Abstract

The study addresses the formation of shear bands in polycrystalline titanium subjected to dynamic deformation at room temperature. Hat-shaped samples were cut from a hot-extruded rod, both along and perpendicular to the extrusion direction, and then deformed at a strain rate of 4.9 × 10³ s⁻¹ using a drop hammer. Structural and textural analyses were performed on the axial sections of the samples using a scanning electron microscope equipped with an electron backscatter diffraction device. Regardless of the initial texture of the samples, a pronounced, oriented rotation of the crystal lattice was observed in grains located within the strain localization region. The primary rotation trend oriented the {0001} planes perpendicular to the shear plane and parallel to the loading direction, with one of the {1−100} planes aligned parallel to the shear plane, whereas a 〈11−20〉 direction, common to both planes, was aligned parallel to the shear direction. This crystal lattice rotation mechanism observed in grains of the strain localization region facilitates slip propagation across grain boundaries without an apparent change in the shear direction.