Magnetic Origin Of TiNb Alloy And The Influence Of Doping Elements On Its Magnetic Properties

Due to their low density,low elastic modulus and good corrosion resistance and biocompatibility,the beta titanium alloys have a broad application prospect as the biological implant materials.Normally,to promote the stability of ? phase and decrease the elastic modulus of the Ti alloys,the d-electron rich transition metals,such as Nb,Mo,Ta,Zr and so on,are added into the titanium alloys to adjust the valence electron concentration of titanium alloys.So,alloying method is an effective way to improve the microstructure and mechanical properties of titanium alloy.It should be noted that,in the ? titanium alloys,the spin coupling between d electrons of Ti atoms and other transition metal elements may make the alloy to exhibit magnetism,,which may cause a directional arrangement of bone cells,and promote the growth of new bone.It is benefit to increase the life span of the implants.In light of it,in this thesis,the magnetic properties of TiNb alloy were studied by the first principles method.The main results are as follows:?1?The effects of Nb atomic content on the magnetic properties of Ti-Nb alloy the ?,?" and ? phases in Ti-Nb alloys were systematically studied by the first principles method based on density functional theory?DFT?.It is found that ?-Ti_0.75Nb_0.25 exhibits a relatively strong magnetism with a magnetic moments of 6.113 ??,while the phases with other Nb contents do not show magnetism.The magnetism of ?-Ti_0.75Nb_0.25 alloy is induced by the spin polarization of the t2 g states of Ti atoms.This result is confirmed by the experiments.?2?The effects of Nb content on the magnetic properties of ?-TiNb was studied systematically by the first principles method based on density functional theory?DFT?.The results show that the magnetism of TiNb alloys increases first and then decreases with Nb content increasing.The alloy with 25 at.% Nb exhibits a strongest magnetic moment,which reaches 6.133 beta.The magnetism of the alloys originates from the coupling between d-electrons of Ti atoms and Nb atoms.Moreover,the effects of Nb,Mo,Ta,Zr additons on the magnetic properties of ?-Ti0.75X0.25?X=Nb,Mo,Ta,Zr?binary alloys were studied.It is found that the magnetic properties of ?-Ti0.75X0.25 are related to the atomic radius of X atom,the smaller the radius of X is,the stronger the magnetism of ?-Ti0.75X0.25 is.?3?The effects of Mo,Sn,Ta,Zr additions on the magnetic properties of ?-Ti_0.75Nb_0.25 were studied.The results show that all the alloys exhibit a magnetic moment,but their moments are less than that of the binary Ti_0.75Nb_0.25 alloy.It may be attributed to the coupling between?Mo,Sn,Ta,Zr?and Nb atoms,which may resulting the decrease of the number of electrons between Ti atoms and Nb atoms.The magnetism of the alloys also originates from the coupling between d-electrons of Ti atoms and Nb atoms.?4?The effects of magnetic atom Fe doping on the magnetic properties of Ti_0.75Nb_0.25 were systematically studied by the first principles method based on density functional theory?DFT?.The results show that the ? phase of Ti0.74Nb0.25Fe0.01 alloy has no magnetism.While ?" and ? exhibit magnetism.However,the three phases in Ti0.6875Nb0.25Fe0.0625 alloy do not exhibit magnetism.The results are confirmed by the experimental tests.