Influence mechanism of the initial dislocation boundary on the adiabatic shear sensitivity of commercial pure titanium

摘要

As-annealed commercial pure titanium was selected as a model material with hexagonal close-packed (hcp) crystalline structure. Dislocation boundaries with different spacing values were prepared by cold rolling at various reductions. The influence mechanism of the initial dislocation boundaries on the adiabatic shear sensitivity of commercial pure titanium was investigated from two aspects: related dynamic mechanical response and dislocation boundary configuration. The geometrically necessary dislocation boundaries (GNBs) with spacing values of 550 nm, 340 nm and 107 nm were induced by cold rolling. The narrower the spacing of the GNBs was, the more sensitive the adiabatic shearing behavior was, which was attributed to the shear stress and adiabatic temperature rise. A narrow spacing of GNBs shortened the mean free path of dislocation slipping; as a result, the deformed resistance and accumulated plastic deformation work became larger. Therefore, the adiabatic temperature rise that was converted from plastic deformation work increased, thereby strengthening the material's adiabatic shear sensitivity.