A number of titanium mechanical properties can be improved by the method developed by Russian researchers for nano-scale grains formation in pure titanium structure. The information on researching structure and properties of nano-scale titanium as well as implants based on it will be published in May issue of the “Russian Nanotechnologies” journal. The effort has been sponsored by the Federal Target Program “Research and academic stuff of innovative R... and analytical departmental target program “Development of scientific p... .
Titanium is one of the most promising materials for making surgical implants – prostheses implantable in the organism, which are used extensively in traumatology. This unique material possesses biocompatibility with organism’s tissues and even accretes with the bone. Although titanium is a sufficiently strong material, in some cases, scientists require higher strength properties. To increase strength, researchers often introduce admixtures, for example, aluminum and vanadium, into pure titanium. However, the indicated alloying elements have detrimental effect on the organism. Therefore, it is necessary to search for new methods to strengthen bio-inactive pure titanium from the point of view of better biological compatibility.
Formation of nano-scale grains via plastic deformation represents a trade-off alternative for pure titanium strengthening. Researchers at the Research-educational and innovative center “Nano-structural materia... and Belgorod State University in cooperation with researchers at the All-Russian Research and Planning Institute of Medical Instruments of Kazan carried out investigations of structure and mechanical properties of such nano-structured titanium.
To create nano-scale grains in titanium structure, the researchers applied an original plastic deformation method, which combines helical and lengthwise rolling. After metalforming by forming rolls was performed, titanium underwent annealing to release internal stress. As a result, grains of various sizes appeared in the structure, including those, which were less than 100 nm, the average dimension of formed grains making 290 nm.
Then specialists compared strength properties of processed unalloyed titanium and aluminum- and vanadium-alloyed titanium. Conducted mechanical tests indicated almost twofold increase in titanium strength as compared to its initial state. Moreover, the obtained values approximated to alloyed titanium strength values.
Finished goods tests, namely tests of titanic screws for traumatology are of interest from practical application point of view. Besides high strength properties, the screws should possess significant torsion plastic deformation. If the screw material is not sufficiently plastic, than screw destruction is possible upon structure assembly under real medical prosthetics operation conditions. As a result, the surgeon will have to drill the remainder (worm gear portion) of the screw out of the bone and to change configuration of installable construction. This procedure leads not only to unplanned increase of operation duration but also to increased risk of incorrect implant functioning. Titanium screw testing has proved that nano-structured titanium possesses extremely high plasticity, maximum twist angle of the sample up to its damage makes 410 degrees. The above result is approximately 60% higher than plasticity value of alloyed titanium.
Titanium strengthening due to nano-scale grain formation in pure titanium is equivalent to strengthening due to alloying elements in terms of mechanical properties values. In the researchers’ opinion, such strengthening method is an adequate substitute for metal alloying.
Source of information:
M.B. Ivanov, Yu. R. Kolobov, E.V. Golosov, I.N. Kuzmenko, V.P. Veinov, D.A. Nechaenko, E.S. Kungurtsev “Mechanical properties of batch-production nano-structural titanium”. Russian Nanotechnologies, Vol. 6, # 5–6.
Mikhail Petrov published by STRF.ru