Study On Properties Of Porous Titanium Alloy And Its Micro-Arc Oxidation Films

Porous titanium and its alloys are widely used in bone tissue repair and replacement,On the one hand,titanium alloy has excellent biocompatibility,low density,high strength and so on.On the other hand,the porous structure makes the the elastic modulus of the implant match with bone, and is good for the transport of nutrients,the ingrowth of biological tissue,shortening the healing time and so on.In recent years,a new type of biomedical porous titanium materials with surface optimization has become a hot research topic in bone repair and replacement materials. However,how to get controlled porosity and excellent surface activity still needs to be studied deeply.In the present study,powder metallurgy along with MAO were used to prepare porous titanium with suitable mechanical properties and surface activation and porous Ti-Sn-Nb alloy, also,the preparation process,mechanical properties and biological activity were studied.Scanning electron microscopy（SEM）, X-ray diffraction（XRD）,universal material testing machine were used to analaze the surface morphology,pore size and its distribution,chemical composition,microstructure and mechanical properties,besides,the apatite-inducing ability was evaluated by simulation body fluid（SBF） immersion test.Results indicated that with the change of the amount of the space holder, the main phase of the porous titanium remained unchanged;Its porosity ranged between 6.9% and 65.7%,and the higher the porosity was,the greater the average pore diameter was;with the increasing of the porosity,the compressive strength decreased and was between 50 and 1558 MPa;when the content of space holder was between 30% and 50%,the elastic modulus of porous titanium ranged between 4.1 and 9.4 GPa,which was very close to the bone’s elastic modulus（2.3²0 GPa） in theory.The porous titanium had the potential to become the artificial bone.In order to improve the surface activity of porous titanium, micro arc oxidation treatment of porous titanium was carried out.TiO₂ and Zn-TiO₂ active films were prepared on the surface of porous titanium samples successfully.The effect of pulse voltage on the surface morphology, phase composition,element content and distribution of the oxide film was studied.It was found that the porous oxide film was formed on the surface of the titanium,with the increasing of pulse voltage,the quantity of pore on the film decreased,but its diameter became larger,the film’s thickness was enhanced,the rutile phase content got higher,and the surface cracks were more obvious.Ca, P and Zn elements were uniformly distributed in the film.The simulated body fluid immersion test showed that the surface of the samples obtained from the micro arc oxidation induced more apatite to deposit,which demonstrated that the micro arc oxidation improved surface biological response.In order to enhance mechanical properties and biological compatibility of titanium alloy with high porosity,biocompatible tin,niobium and titanium powder were used as raw material to prepare highly porous Ti-Sn-Nb alloy.When the content of space holder was 50%,the porosity of the porous titanium alloy was 70%;Nb had a significant impact on mechanical properties of the alloy,when its content reached 7%,compressive strength of the porous titanium alloy increased rapidly from 3.5 MPa（niobium free alloy） to 30.8 MPa.Besides,alloy elements were uniformly distributed in titanium matrix.