| Titanium(Ti)and Ti alloys exhibit excellent mechanical properties,good biocompatibility and excellent corrosion resistance,so they are widely used as biomedical materials.Compared with the previous two generations of medical titanium alloys,the third-generation β-type biomedical titanium alloys,especially Ti-Nb-based and Ti-Ta-based alloys,present improved overall performance significantly.Powder metallurgy takes the advantages of high raw material utilization ratio and near-net shape forming,and is especially suitable for the preparation of Tibased implants with complex shapes.Due to the high melting points and the low diffusion coefficients of the refractory metals such as Nb and tantalum(Ta),a high sintering temperature and long sintering time is required when Ti-Nb-based and Ti-Ta-based alloys prepared by powder metallurgy.It would not only influence the mechanical properties of the material,but also greatly increase the cost and cycles of production.Aiming at the above-mentioned problems,this work takes Ti-Nb-based alloy as an example.Iron(Fe)is often used for activation sintering of titanium alloys as a non-toxic and cheap β-stabilizing element.Adding Fe element into Ti-22 Nb alloy can leads to the formation of the Ti/Fe eutectic liquid phase,and thereby promoting the rapid diffusion of Nb.This study demonstrates the promotion of the diffusion of Nb particles by the eutectic liquid obtained during the sintering process of Ti-Nb-Fe alloy by using the "powder spreading" experiment.The wetting behavior of the eutectic liquid phase on Ti and Nb matrix at continuous temperature is studied by using the high temperature contact angle test.The results show that within the test temperature range,the Ti/Fe eutectic liquid exhibits a better wetting effect on Nb than that of Ti.The sintering parameters of Ti-Nb-Fe alloy are guided by the Ti/Fe eutecticNb pseudo-binary phase diagram as well as the high-temperature contact angle results.The samples are characterized by optical microscope,scanning electron microscope,energydispersive spectroscopy X-ray diffractometer.The influence of sintering parameters,Fe content and Fe powder size on the homogenization and densification behavior of Ti-Nb-Fe alloys are studied.The Ti-22Nb-x Fe alloy sintered at 1200 °C /30 min+1250 °C /2 h can be homogenized when the Fe content is higher than 3 wt.%.However,the Fe content higher than 8 wt.% could lead to excessive porosity,and in addition,larger-sized Fe powder may impair the homogenization and densification of the Ti-Nb-Fe alloy.The mechanical properties of Ti-NbFe alloys are analyzed by tensile tests.It is found that the addition of Fe could lead to brittle fracture of the sample.The biocompatibility of Ti-Nb-Fe alloys is also investigated by using the protein adsorption,cell adhesion and cell proliferation,and both Ti-Nb-Fe alloy and Ti-Nb alloy exhibit good biocompatibility. |
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