It is known that titanium and its alloys are one of the promising materials in the industry, especially in medicine, due to their excellent biocompatibility and corrosion resistance. The latest modern equipment and instruments used in traumatology, orthopedics, dentistry, etc. demand increasingly higher mechanical properties for materials. In comparison with commercially pure titanium, alloys do not have such high corrosion-resistant properties and biocompatibility. In this regard, improving the mechanical characteristics of a pure material is an urgent issue. The authors studied the effect of annealing on the structure and properties of commercially pure grade 4 titanium in the coarse-grained and ultrafine-grained states. The ultrafine-grained state was obtained using high-pressure torsion (HPT) under the pressure of 6 GPa at N=10 revolutions at room temperature. In the microstructure investigated using transmission electron microscopy, the authors could detect particles of precipitated phases after annealing, which had different morphologies. Deformation leads to an increase in the precipitated particles after annealing. The authors carried out an X-ray phase analysis, which showed the approximation of the lattice parameters of the α-phase after deformation and annealing at 700 °C to the values of the parameters of pure titanium. Thus, aging processes occur in the material, accompanied by the decomposition of the supersaturated solid solution and the release of particles of the second phase. The paper shows the results of titanium microhardness measurements in different states. The combined treatment, consisting of HPT at N=5 revolutions, annealing at 700 °C, and additional HPT deformation at N=5 revolutions, allowed obtaining the record strength for commercially pure grade 4 titanium.
Strength and torsion fracture mechanism of commercially pure titanium with ultrafine-grained structure
