Tkach D. Improving of the performance properties titanium VT1-0 products of submicrocrystalline structure with twist extrusion

The processes is the of the submicrocrystalline structure formation of products made from titanium VT1-0 at intensive plastic deformation are the object of study. The subject of the study is the establishing of the nature of influence of twist extrusion and heat treatment on processes of grain fragmentation, fine structure and physico-mechanical properties of technical pure titanium. The purpose of the study is to establish the nature of structure formation and exploitation properties increase of titanium VT1-0 at thermo-deformation twist extrusion processing method aiming to improve the operational reliability of medicine and technic products. The research methods are X-ray diffraction studies, metallography, methods mechanical properties studies, methods of mathematical modeling, numerical methods of the theory of elasticity. For the first time the results showed that during intensive plastic deformation grain structure fragmentation processes are accompanied with changes of lattice parameter and formation of axial texture. Experimental data specified by acceleration of the grain structure reorientation and reduction of recrystallization beginning temperature to 385 ° C level resulting of five cycle deformation. A heat treatment regime of products at 300 ° C for 1 hour was proposed. Studing linearized hardening curve, it is established the fact of three distinct linear portions formation, indicating a gradual decrease of hardening intensity with increasing the number of deformation cycles. It is established that 5-cycle twist extrusion provides the highest hardening indices and the lowest dispersion of angle coefficient at cross section. Based on the physical concepts and the theoretical study, the model of fatigue fracture of metals and alloys was developed; and on the basis of this model a complete fatigue curve of technical pure titanium submicrocrystalline condition was obtained. It is established that titanium VT1-0 in submicrocrystalline state meets the necessary strength conditions and can be used in the production of load-bearing elements of the endoprothesis. At the "Traumatology and Orthopedics" department of Dnepropetrovsk Medical Academy expert verification of prospects for application of commercially pure titanium implants in submicrocrystalline state and other products of orthopedics and traumatology was given. In Zaporozhye National Technical University the results are used in the educational process. The scope of application is medicine and chemical industry.