Effects of Initial Micro-Structures on Deformation Behaviors of Commercial Pure Titanium

In this paper, effects of initial micro-structures on deformation behaviors of commercial pure titanium were elaborated by investigating the evolution of dislocation boundary and its adiabatic shear sensitivity. At the low to medium stain rates, the main plastic deformation mechanism of as-annealed commercial pure titanium is dislocation slipping. Meanwhile, geometrically necessary boundaries (GNBs) with different directions are generated and crossed with each other. However, new dislocation boundaries are formed in as-cold rolled plates, which are parallel to the initial ones induced by cold rolling. When the strain rate is up to 1000 s-1, the initial dislocation boundary playes an adverse role in the adiabatic shear sensitivity of commercial pure titanium. The adiabatic shear band is the high-speed deformation characteristic micro-structure in commercial pure titanium. In addition, dynamic recrystallized grains are generated in the center of an adiabatic shear band, which is consistent with the sub-grain rotation mechanism.

The Effect of Initial Microstructure on the Dynamic Mechanical Behavior of Titanium Plate at Different Strain Rates

The dynamic mechanical property and microstructure evolution of commercial pure titanium with initial lamellar dislocation boundary structures were studied at different strain rate compression. The experiments were conducted to the cylindrical specimens using Gleeble-3500 thermal mechanical simulation machine at room temperature. With increasing of the strain rate, strain rate strengthening effect was found in the material. New dislocation boundary structures along impact direction were generated which perpendicular to initial dislocation boundary. Then the S bands boundary structure was formed by interaction between new and initial dislocations. It can be supposed that initial dislocation boundary are sheared and kinked by new dislocation slipping.