| Titanium alloy has good biocompatibility,mechanical properties and processing performance and it is widely used in clinical medicine.Ti-24Nb-4Zr-7.9Sn?TNZS?is a new beta titanium alloy developed in China,the mechanical properties and biological properties of TNZS are very prominent,it has broad prospects in the preparation of artificial implant.This paper uses high-energy ball milling and cold pressing sintering to prepare TNZS,5wt.%Cu/TNZS,5wt.%Ag/TNZS and 5wt.%Co/TNZS materials and studies their microstructure,surface roughness,micro hardness,elasticity modulus,corrosion resistance,tribological properties,and histocompatibility in vitro.The addition of Cu,Ag and Co has changed the microstructure and comprehensive properties of the TNZS based materials.The concrete conclusions are as follows:Study on the micro-structure and pore characteristics of TNZS,5wt.%Cu/TNZS,5wt.%Ag/TNZS and 5wt.%Co/TNZS mixed powder prepared by high-energy ball milling and cold pressing sintering.The results indicated that,there were Alpha-Ti phase,beta-Ti phase and single substance Sn in TNZS,5wt.%Cu/TNZS,5wt.%Ag/TNZS and5wt.%Co/TNZS mixed powders after high-energy ball milling.The existence of high temperature beta-Ti indicated that there were solid solutions.In addition,Ti-Sn compounds were detected in four kinds of composite powders,indicating that four kinds of mixed powders have been mechanically alloyed to a certain extent.The XRD studies of TNZS,5wt.%Cu/TNZS,5wt.%Ag/TNZS and 5wt.%Co/TNZS samples after cold pressure sintering showed that all of the four samples contain alpha-Ti phase,beta-Ti phase and SnTi3 phase.In addition,CuTi,Cu10Sn3,Sn3Ti2,Sn3Ti5 phase,Ag4Sn phase and CoTi,CoTi2 phase were also detected in 5wt.%Cu/TNZS,5wt.%Ag/TNZS and5wt.%Co/TNZS respectively.At the same time,the results of EDS test also showed that the distributions of part components in the four kinds of samples after cold pressure sintering were not uniform,and the aggregations of Nb and Zr were more obvious.On the whole,adding 5wt.%Cu,Ag and Co to TNZS based materials can reduce the grain size and improve the uniformity of the tissue.In addition,the apparent porosity of TNZS,5wt.%Cu/TNZS,5wt.%Ag/TNZS and 5wt.%Co/TNZS after cold pressure sintering were measured by Archimedes drainage in the experiment.The results showed that the porosity of TNZS was the highest,which was 9.93%.After adding 5wt.%of Cu,Ag and Co,the porosity of the corresponding samples were 5.31%,7.71%and 5.80%respectively,and the pore morphology of 5wt.%Co/TNZS and 5wt.%Cu/TNZS were relatively regular.The surface roughness,the Vickers hardness,the modulus of elasticity and the characteristics of electrochemical corrosion about the four materials were compared and analyzed.The test results showed that the surface roughness Ra values of TNZS,5wt.%Cu/TNZS,5wt.%Ag/TNZS and 5wt.%Co/TNZS were 0.5136?m,0.1583?m,0.3372?m,0.2807?m respectively.The surface roughness of TNZS was the highest,while the surface roughness of 5wt.%Cu/TNZS was the lowest.In addition,the mean surface micro-hardness values of the four materials were 560.1 HV,747.7 HV,505.4 HV and 1045.6 HV respectively.The mean surface micro-hardness of 5wt.%Ag/TNZS was the lowest,which was 9.77%lower than that of TNZS.While the mean surface micro-hardness values of 5wt.%Cu/TNZS and 5wt.%Co/TNZS increased by 86.68%and33.49%respectively,compared with that of TNZS.At the same time,the elastic modulus of TNZS,5wt.%Cu/TNZS,5wt.%Ag/TNZS and 5wt.%Co/TNZS were 45.21 GPa,82.15GPa,40.98 GPa and 73.69 GPa respectively.After adding Cu and Co,the modulus of elasticity increased in varying degrees.While the addition of 5wt.%Ag to TNZS based materials can reduce the elastic modulus to some extent.In addition,the self corrosion potentials of the four materials were-0.97 V,-0.97 V,-0.95 V and-0.71 V respectively,and their self corrosion current densities were 4.17×10-66 A·cm-2,2.34×10-66 A·cm-2,1.91×10-6A·cm-2,1.29×10-7A·cm-2.It could been seen that the corrosion resistance of5wt.%Co/TNZS was the best,5wt.%Ag/TNZS was the second,and the corrosion resistances of 5wt.%Cu/TNZS and TNZS were poor.The tribological behaviors of four biological titanium based materials under dry friction and artificial body fluid were discussed.The experimental results showed that the average friction coefficients of Ti alloy TNZS,5wt.%Cu/TNZS,5wt.%Ag/TNZS and5wt.%Co/TNZS under dry friction conditions were 0.5035,0.4972,0.4726 and 0.4913respectively.The surface abrasions of TNZS and 5wt.%Cu/TNZS were serious,while the surface abrasions of 5wt.%Ag/TNZS and 5wt.%Co/TNZS were slight.According to the EDS,the wear mechanism of TNZS was mainly abrasive wear,and oxidation wear and adhesive wear were the secondary mechanisms.While the abrasion mechanisms of5wt.%Cu/TNZS,5wt.%Ag/TNZS and 5wt.%Co/TNZS gave first place to fatigue wear and abrasive wear,with a certain degree of oxidation wear and adhesive wear.Under the condition of SBF,the average friction coefficients of TNZS,5wt.%Cu/TNZS,5wt.%Ag/TNZS and 5wt.%Co/TNZS were 0.3176,0.3912,0.3498 and 0.2854respectively,which decreased by 36.92%,21.32%,25.98%and 41.91%compared with dry friction conditions.And the wear resistance of 5wt.%Co/TNZS was the best,5wt.%Ag/TNZS was the second,and the friction and wear properties of TNZS and5wt.%Cu/TNZS were poor.According to the results of EDS analysis,the abrasion mechanisms of the four materials gave first place to fatigue wear and abrasive wear,with a certain degree of oxidation wear and adhesive wear.The cell proliferation and cell attachment ability of the four Ti alloys were investigated and the cytotoxicity was evaluated.The results of cell proliferation experiment showed that at the early stage of cultivation?1 d,3 d?,5wt.%Co/TNZS surface was most conducive to promoting cell attachment,while in the late stage of cultivation?5 d,7 d?,the 5wt.%Cu/TNZS and 5wt.%Ag/TNZS surfaces were more favorable for attachment of Osteoblast.Moreover,CPIR values of 5wt.%Cu/TNZS,5wt.%Ag/TNZS and 5wt.%Co/TNZS when cultured 3 d,5 d and 7 d were lower than that of TNZS,indicating that adding 5wt.%Cu,Ag or Co can increase osteoblast proliferation ability to some extent.Meanwhile,cell attachment experiment showed that the morphology and extension of osteoblasts on the surface of 5wt.%Ag/TNZS were the best,followed by 5wt.%Co/TNZS,while the surface attachment ability of TNZS and5wt.%Cu/TNZS cells were poor.The cytotoxicity test results showed that the cytotoxicity grade of the four titanium alloys were all 2 grade,which accorded with the cytotoxicity requirement of materials in the national standard for biological performance evaluation of medical devices.The results of this study first discovered that compared with Ag and Co,Cu has a more prominent performance in reducing the porosity and improving wear surface roughness of TNZS based materials.And Ag is better in improving the histocompatibility in vitro of the materials and reducing the modulus of elasticity.In addition,the effects of Co on improving the micro-hardness of materials and improving the corrosion resistance and wear resistance of the materials are more remarkable than that of Cu and Ag. |
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