NANOSTRUCTURED MATERIALS Progress in hydrostatic extrusion of titanium

At the beginning of the present century it has been demonstrated that nanocrystalline titanium (NC-Ti) can be fabricated by hydrostatic extrusion (HE) which is one of the severe plastic deformation method. NC-Ti obtained in such a way exhibited excellent mechanical properties. The influence of HE on the microstructure and mechanical properties of titanium Grade 2 was first analyzed in 2005. In this study the progress in HE of titanium has been described. However, there are tribological and technological challenges encountered in HE of titanium. They can practically be eliminated by modifying the surface of Ti billets with aluminum coatings. Another important issue in extrusion is the optimum value of the accumulated strain necessary for grain refinement of titanium. Our results have shown that this value must exceed 3 to obtain nanocrystalline Ti. The results obtained indicate that HE permits producing NC-Ti rods with the diameter up to 10 mm.