Isotropic titanium for biomedical applications after severe plastic deformation.

The pure titanium is very good material for implants due to their stable chemical properties and good biocompatibility. However, its relatively low mechanical properties limits its applicability (UTS = 345 MPa, YS = 275 MPa). Currently usted titanium alloys containing toxic alloying additives, such as aluminium, vanadium, niobium, etc. The subject of the study was commercially pure titanium CP Ti (grade 2), which, after generating an isotropic, highly refinement structure and after significantly increasing strength, can replacing the above alloys, eliminate the unhealthy alloy additions and will have practical application in implantology.

Obtaining titanium with isotropic structure and enhanced mechanical properties is possible due to combination of two methods of severe plastic deformations: hydrostatic extrusion (HE) and equal-channel angular pressing (ECAP) with optional post-deformation heat treatment. The appropriate combination of these processes significantly increas mechanical properties (UTS = 750 MPa, YS = 670 MPa) and reduce the material's morphological texture. The characteristic feature of the HE process is the generation of a structure with grains elongated in the direction of extrusion. This results in anisotropy of mechanical properties of the titanium after the deformation process aprox 15%. The characteristic feature of the ECAP process in the non-uniform distribution of plastic deformations and shear stresses in the plastic deformation zone. This is favourable to structural and mechanical heterogeneity of the deformed material. Application of the ECAP method before the HE process allowed for preliminary refinement of titanium microstructure, which reduced the occurrence of morphological texture and related anisotropy of mechanical properties after the HE to a level of about 2%.

High strength and the lack of structural and mechanical anisotropy in titanium enable its use for medical implants.