Microstructures And Properties Of New Low Modulus Medical Titanium Alloys

Titanium alloys have high specific strength,low modulus of elasticity,good corrosion resistance and biocompatibility,and are suitable for use as medical implant alloys.In recent years,the stress shielding effect caused by the difference of elastic modulus between implanted alloy and human bone is still a major problem in orthopedic implantation.In addition,the increase of plasticity and strength is beneficial to improve the processing and service properties of titanium alloy.The antibacterial and biocompatibility of titanium alloy can be improved by adding certain elements.Therefore,three kinds of medical β-titanium alloys,Ti-Nb-Zr-Sn-Fe alloy with low elastic modulus and high plasticity,Ti-Nb-Zr-Fe alloy with low elastic modulus and high yield strength and Ti-Fe-Cu-Sn-Nb alloy with low elastic modulus and good biological properties,were designed and prepared in this paper.The microstructure,mechanical properties,biocompatibility and antibacterial properties of some alloys were studied.In this paper,the composition of the alloy with low elastic modulus was designed according to the molybdenum equivalent theory,D-electron theory and valence electron theory.The β-state alloy was obtained by solid solution and water quenching at 800 ℃after multi-pass hot rolling in a non-consumable vacuum melting furnace.The tensile mechanical properties were tested by universal mechanical testing machine.The microstructure,microstructure and fracture morphology of the alloy were observed by metallographic microscope(OM),scanning electron microscope(SEM),transmission electron microscope(TEM)and X-ray diffraction(XRD).The antibacterial properties of the samples were tested by Escherichia coli test,and the biocompatibility of the alloy was tested by leaching solution test.The tensile test results of Ti-Nb-Zr-Fe β alloy show that the elastic modulus of the alloy decreases significantly with the increase of Nb content,and the elastic modulus can be as low as 61 GPa.The yield strength of the alloy is 779-890 MPa,the tensile strength is 791-933 MPa,and the plastic elongation is 12-22%.Ti20Nb15Zr2 Fe has the best properties with an elastic modulus of 61 GPa,a yield strength of 779 MPa and an elongation of 18%.Thelow elastic modulus of the alloy is caused by the high bond energy and d orbital energy between alloying elements and the phase instability of the alloy.Ti-Nb-Zr-Sn-Fe-series β alloys have elastic modulus of 65-69 GPa,yield strength of570-620 MPa,tensile strength of 780-830 MPa,and plastic elongation of 33-42%.Ti13Nb7Zr5Sn2 Fe alloy has an elastic modulus of 69 GPa,a yield strength of 630 GPa and a fracture strength of 830 GPa,and a ductility of 41.6%.The Nb and Zr elements in the alloy have higher Bo and Md values and higher contents,which can significantly reduce the elastic modulus of the alloy.The high plasticity of alloy mainly comes from the effect of transformation induced plasticity(TRIP).The Ti-Fe-Cu-Sn-Nb β alloy has an elastic modulus of 82-85 GPa,a tensile strength of932-1035 MPa and a plastic elongation of 13-15%.Biological experiments showed that the toxicity rating of the alloys was 0,and the antibacterial rate of the alloys was as high as 77%.The mechanical properties,antibacterial properties and biocompatibility of the alloy are derived from the addition and optimization of Cu,Nb,Sn and Fe.