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Titanium Based Alloys with Shape Memory Effect

#G-1449


Development of Multi-Component Nickel-Free Titanium based Alloys with Shape Memory Effect for Biomedical Application

Tech Area / Field

  • MAT-ALL/High Performance Metals and Alloys/Materials

Status
3 Approved without Funding

Registration date
29.08.2006

Leading Institute
Georgian Technical University, Georgia, Tbilisi

Collaborators

  • Scandinavian Memory Metals AB, Sweden, Saltsjobaden\nUniversity of Tsukuba / Institute of Material Science, Japan, Tsukuba

Project summary

Objective of the project is development of multi-component nickel-free titanium alloys with shape memory effect (SME) and superelesticity (SE) at body temperature, suitable for biomedical application (the alloys must be physiologically and biologically compatible with the ‘soft’ and the bone tissue). The alloys must be physiologically and biologically compatible with ‘soft’ and bone tissue. The alloys will be Ti-Nb, Ti-a, Ti-Ta-Nb based, for additional alloying Zr, Ga, Ge, Si, Cr, Mo, V, Fe, B, Al, Sn, O will be used. Developed new alloys may act as alternative to ‘nitinol’ (Ni-Ti), the alloy rather widely used in medicine but potentially toxic because of the high (50%) nickel content. Pure nickel, depending on the thermal treatment regime of an alloy, may isolate in the surface TiO2 layer. The new alloys will have fundamental advantage over such traditional materials as stainless steel, which does not show either SME or SE.

The SME is ability of material deformation at a certain temperature, to restore its initial shape while heating. In case of the stable SME, deformation-recovery cycle by heating can be reiterated.

SE is complete recovery, in a certain temperature interval, of the shape of deformed material after removal of external deforming force. The SE recoverable deformation differs from an ordinary elastic deformation by its mechanism and exceeds it many times higher.

SME enables to use the alloys for development of arrangements (cardiovascular stents, blood filters) which, when compactly deformed and introduced through catheter into the body self-expand after heating to the body temperature (370C). SME and SE enable operation of different orthopaedic implants, spinal vertebrae spaceres and allow dynamic contact of the medical appliances with tissue. Titanium alloys are biocompatible with tissue and do not cause rejection as in case observed in case of the stainless steel.

The works on development of the nickel-free titanium alloys are under way in the Institute of Material Science, University of Tsukuba (Japan), Precision and Intelligence Laboratory, Tokyo Institute of Technology (Japan), Department of Material Science Engineering, Kumamota University (Japan), Memory Corporation, Connecticut (USA).

Results are being published in scientific periodicals such as Materials Science and Engineering, Acta Materialia, Materials Transactions, etc., as well as presented at International conferences (ICOMAT, SMST, MRS, etc.)

The research of titanium alloys in Georgian Technical University dates back to the 80-ies. Three authorship certificates were obtained on the methods for preparation of some SME alloys. From 2002 to 2005 the project on development of titanium alloys with maximum manifestation of high temperature SME (under the funding from ISTC, project#G-499) was carried out by the team of researches. Some results were presented at International conferences (E-MRS Fall Meeting September 2005, proceedings C-05, p.68, Warsaw, Poland; MMS-2005 Modern Material Science: Achievements and Problems, proceedings, p.130, Kiev, Ukraine; 43 International Conference: Actual Problems of Strength, October 2005, proceedings, pages 173, 176, 202, Vologda, Russia.) and are in press (International Journal of Applied Electromagnetics and Mechanics, 21 (2005), 1-2).

Development of the new titanium based alloys will contribute to development of non-toxic nickel-free titanium alloys for biomedical application.

Presented project conforms with the tasks of ISTC to direct research on peaceful objectives of healthcare and will establish creative contact between the scientists of the Georgian Technical University with the scientific centres abroad.

Development of the new alloys will be grounded on the fact that the temperature of SME and SE manifestation and mechanical properties of the alloys depend on the type and concentration of elements in the alloy. During the study composition providing SME and SE at body temperature and elastic modulus close to the average elasticity of uneven bone tissue (to avoid painful irritation of orthopaedic implants) will be experimentally selected (method of successive selection)

Special attention will be paid to stability of the SME and SE manifestation temperature and stability towards multiple deformation-temperature and mechanical (strain-stress) cycling. The works will include forecasting of initial composition of alloys, look into the influence of constituent component concentration on SME and SE manifestation temperature. Dependence of the degree of the shape recovery on initial deformation will be determined, elastic modulus and strength of alloys measured. Results will be analysed. Based on that, subsequent adjustment (possibly multiple) of composition of alloys will be done. Each stage of successive adjustments will include preparation of the new composition alloys and study of their properties.

SME and SE will be tested on tensile, bending and torsion deformation. Alloys most perspective for biomedical use will be checked on biocompatibility with living tissue. Comparative analysis with nitinol data will be provided.

Creative contact with collaborator of the project will consist in information exchange, meetings/discussions and some joint control measurements.


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