Preparation And Study On The Crystallization Kinetics And Biomedical Properties Of Ti-Zr-Si-based Amorphous Alloys

Ti-based amorphous alloys are a kind of materials with high specific strength,excellent corrosion resistance and biocompatibility and low elastic modulus.They have a wide application prospect in the field of biomedical implant materials.Biomedical Ti-based amorphous alloys can be roughly divided into four categories:Ti-Zr-Cu-Pd,Ti-Cu-Zr-Fe-Sn-Si,Ti-Zr-Si and other biomedical Ti-based amorphous alloys.Among them,Ti-Zr-Si-based amorphous alloys contain no toxic or allergenic elements such as Cu and Ni,so they become the key research direction of biomedical Ti-based amorphous alloys.However,the glass forming ability of Ti-Zr-Si-based amorphous alloys is relatively poor,and only micron-thick ribbon samples can be prepared,which seriously restrict their application as biomedical materials.Based on the design principle of biomedical Ti-based amorphous alloys,a series of Ti-Zr-Si-based amorphous alloys are designed and successfully prepared in this dissertation.The glass forming ability of Ti-Zr-Si-based amorphous alloys is evaluated by the concept of glass forming stability,and the crystallization kinetics are systematically studied to reveal the effects of alloying elements on their thermal stability and glass forming ability.Finally,the elastic modulus of Ti-Zr-Si-based amorphous alloys,their corrosion resistance and the propensity of hydroxyapatite formation in fluids simulating human body environment are preliminarily characterized.The research contents of this dissertation provide a preliminary exploration for the potential preparation of large-size Ti-Zr-Si-based amorphous alloys by additive manufacturing technology.The main results of this dissertation are as follows:（1）Based on“Inoue’s three empirical rules”,“deep eutectic principle”,“confusion principle”and the principle of not using toxic or allergenic elements and precious metal elements,this work,with Ti₄₂Zr₄₀Si₁₅Ta₃ amorphous alloy as the initial composition,selects Sn,Ge,Ga and B as alloying elements.Ti₄₂Zr₄₀Si₁₅Ta₃,Ti₄₂Zr₃₉Si₁₅Ta₃M₁（M=Sn,Ge）,Ti₄₂Zr₄₀Si₁₅Ta_3-xSn_x（x=1,2,3）,Ti₄₂Zr₄₀Si_15-xSn₃Ge_x（x=1,3,5）,Ti₄₂Zr₄₀Si₁₂Sn₃Ga₃ and Ti₄₂Zr₃₉Si₁₀Sn₃Ge₅B₁ alloy ribbons are prepared by arc-melting and melt spinning.XRD results show that ribbons of Ti₄₂Zr₄₀Si₁₅Ta₃,Ti₄₂Zr₃₉Ta₃Si₁₅Ge₁,Ti₄₂Zr₄₀Si₁₅Ta_3-xSn_x（x=1,2,3）and Ti₄₂Zr₄₀Si_15-xSn₃Ge_x（x=1,3,5）can be formed in completely amorphous state.The results of thermal analysis show that the reduced glass transition temperatures T_rg of the above Ti-Zr-Si-based amorphous alloys are all between 0.45 and0.48（<2/3）,and theγparameters are all between 0.351 and 0.364（<0.4）,which indicate that their glass forming ability is limited.Based on these results,the concept of glass forming stability of alloys is put forward,and the glass forming stability of amorphous alloys is characterized by detecting the amorphous structures in different positions of alloys ribbons.It is found that Ti₄₂Zr₄₀Si₁₅Ta₃,Ti₄₂Zr₃₉Ta₃Si₁₅Ge₁,Ti₄₂Zr₄₀Si₁₅Sn₃ and Ti₄₂Zr₄₀Si₁₀Sn₃Ge₅ have good glass forming stability.However,all experiments to prepare rod-shaped amorphous samples with a diameter of 1.5 mm are unsuccessful,which once again shows that the above-mentioned Ti-Zr-Si-based amorphous alloys have poor glass forming ability.（2）In order to reveal the influence of alloying elements on the glass forming ability of Ti-Zr-Si-based amorphous alloys,the crystallization kinetics of Ti-Zr-Si-based amorphous alloys in isothermal process and continuous heating process are studied with Ti₄₂Zr₄₀Si₁₅Ta₃,Ti₄₂Zr₄₀Si₁₅Sn₃and Ti₄₂Zr₄₀Si₁₀Sn₃Ge₅ amorphous alloys with better glass forming stability.The activation energy E_c1 of Ti₄₂Zr₄₀Si₁₅Ta₃,Ti₄₂Zr₄₀Si₁₅Sn₃ and Ti₄₂Zr₄₀Si₁₀Sn₃Ge₅ amorphous alloys during isothermal crystallization is 259.89±19.45 k J/mol,262.39±15.80 k J/mol and 359.25±17.21 k J/mol,respectively.Their Avrami exponents n are 2.54～2.90,2.72～3.19 and 2.80～3.35,respectively.These results show that during isothermal annealing,the nucleation processes of the 3 amorphous alloys are almost completed in the incubation period,and the isothermal crystallization peak range mainly consists of the crystal growth process controlled by the interface.In the continuous heating process,the crystallization activation energy E_c2 of Ti₄₂Zr₄₀Si₁₅Ta₃,Ti₄₂Zr₄₀Si₁₅Sn₃ and Ti₄₂Zr₄₀Si₁₀Sn₃Ge₅ amorphous alloys is 535.84±27.35 k J/mol,660.46±42.15 k J/mol and 473.65±48.04 k J/mol,respectively.The glass transition activation energy E_g is 768.96±53.54 k J/mol,935.57±66.93 k J/mol and 495.51±14.88 k J/mol,respectively.The addition of Sn increases the contribution of nucleation activation energy to crystallization activation energy E_c2 of Ti-Zr-Si amorphous alloys during continuous heating,and thus increases crystallization activation energy E_c2,which indicates that Sn is beneficial to improve the glass forming ability of Ti-Zr-Si amorphous alloys.The addition of Ge increases the activation energy E_c1 of crystallization of Ti-Zr-Si amorphous alloys in isothermal process,which indicates that Ge is beneficial to improve the thermal stability of Ti-Zr-Si amorphous alloys.（3）The biomedical performances of Ti₄₂Zr₄₀Si₁₅Ta₃,Ti₄₂Zr₄₀Si₁₅Sn₃ and Ti₄₂Zr₄₀Si₁₀Sn₃Ge₅amorphous alloys are preliminarily characterized,including the elastic modulus of the amorphous alloys,the corrosion resistance and the propensity of hydroxyapatite formation in fluids simulating human body environment.The nanoindentation tests show that the elastic moduli of Ti₄₂Zr₄₀Si₁₅Ta₃,Ti₄₂Zr₄₀Si₁₅Sn₃ and Ti₄₂Zr₄₀Si₁₀Sn₃Ge₅ amorphous alloys are 85.2±12.5 GPa,81.7±14.3 GPa and 96.3±7.1 GPa,respectively,which are lower than those of traditional biomedical implant materials.In SBF and Hank’s solution,Ti₄₂Zr₄₀Si₁₅Ta₃,Ti₄₂Zr₄₀Si₁₅Sn₃ and Ti₄₂Zr₄₀Si₁₀Sn₃Ge₅ amorphous alloys show obvious passivation areas,low corrosion current density（less than 50 n A/cm²）and high corrosion potential.The corrosion resistance of Ti-Zr-Si-based amorphous alloys in Hank’s solution is comparable with that of Ti-Fe-Si-based amorphous alloys,and better than that of cp-Ti.SEM patterns,EDS and XRD analyses show that after being cultured in SBF at 37℃for 14 days,after hydrothermal-electrochemical and pre-calcification treatment,hydroxyapatite was formed on the surfaces of Ti₄₂Zr₄₀Si₁₅Ta₃,Ti₄₂Zr₄₀Si₁₅Sn₃ and Ti₄₂Zr₄₀Si₁₀Sn₃Ge₅ amorphous alloys and cp-Ti.Moreover,the number and size of hydroxyapatite pellets on the surfaces of the three amorphous alloys was larger than that of cp-Ti.This indicates that Ti-Zr-Si-based amorphous alloys have good hydroxyapatite formation ability and are expected to be applied in biomedical implant field.