Rate sensitivity and work-hardening behavior of an advanced Ti-Al-N alloy under uniaxial tensile loading

In the present work, titanium alloys doped with different amounts of impurity solutes were studied as regards their strain rate sensitivity, work-hardening and fracture manner. The experimental results revealed a transition of both the strain hardening behavior and fracture manner with increasing the impurity content. Namely, the low impurity content Ti exhibited features of intergranular crack, whereas the high impurity content Ti showed transgranular cracking instead. In addition, the physical activation volumes were found to reduce with the impurity content, which is attributed to both dislocation pinning and solute drag effects. A constitutive model was proposed to understand the mechanical behavior of the materials. The highlights of the model are of separating deforming grains into plastic and elastic groups and of giving them different properties. To describe the volume of grains changing from elastic to plastic deformation with strain, a controlling function was applied based on an empirical analysis. It turns out that the proposed model predicted stress-strain curves in well agreement with the experimental results.