| As biomedical implanting materials, Titanium and its alloys have a broad application prospect for their good biological compatibility, excellent corrosion resistance and mechanical properties. Compared with the crystalline counterparts, the titanium based amorphous alloys exhibit relatively low elastic modulus, extremely high strength and excellent wear and corrosion resistance, which make them have a potential to be used the biomedical materials. However, there are at least two problems which limit the amorphous titanium alloys to be in practical application. One is that the currently developed titanium alloys with high glass formation ability(GFA) usually contain some toxic elements to human body, while the toxic element-free alloys exhibit a low GFA, and thus it is hard to be obtained the bulk amorphous alloys with a large size. Another is that the titanium based amorphous alloy almost has no plasticity at room temperature. Therefore, to develop new toxic element-free titanium amorphous alloys with the high GFA and make them to be in a bulk form with big size prepared into large size, and further to improve the room temperature plasticity of the amorphous alloys,are important to promote the Ti-based amorphous alloys to be in the practical us as the implanting materials.In light of these above, in this thesis, we designed two kinds Ti-amorphous alloy systems without toxic elements, Ti-Zr-Ta-Si-Sn and Ti-Zr-Ta-Si-Nb, based on the theoretical analysis of the amorphous alloy formation ability. The amorphous Ti-Zr-Ta-Si-Sn alloy was prepared by using melt-spinning(MS) method, and the Ti-Zr-Ta-Si-Nb alloy with high strength was obtained by water-cooled copper casting method. The effects of the Sn or Nb elements addition on the amorphous formation ability, corrosion resistance and mechanical properties were studied. Moreover, we prepared the bulk titanium based amorphous alloys and their composites by using powder metallurgy through high pressure sintering. The influences of the processing parameters on the microstructure, thermodynamic behavior and mechanical behavior of the Ti base amorphous alloys and their composite materials were investigated.The main conclusions are summarized as follows:(1) A new toxic element-free Ti-Zr-Ta-Si-Sn alloy system was developed, and the influences of Sn addition on the GFA, the thermodynamic behavior and corrosion behavior of(Ti60Zr10Ta15Si15)100-xSnx(x=0, 4, 8 at. %) alloy were investigated. The results show that, the(Ti60Zr10Ta15Si15)100-xSnx(x=0, 4, 8 at. %) alloy in fully amorphous structure can be successfully obtained by MS method. The addition of Sn slightly decreases the GAF but increases the corrosion resistance of the alloy by promoting the formation of the soundpassivation film on the surface of the amorphous alloy; The Sn addition also has an important influence on the mechanical properties of the amorphous alloys, including the micro hardness and elastic modulus. The change of the free volume of the amorphous alloy system caused by the addition of Sn may responsible for the change of the mechanical properties of the amorphous alloys.(2) By adding Nb to partly replace Ta in the Ti-Zr-Ta-Si alloys, the amorphous alloy system Ti-Zr-Ta-Si-Nb was developed, and the rods of the Ti60Zr10Si15Ta15-xNbx(x=0, 3, 7, 11 at. %) alloys were prepared by the water-cooling copper suction casting method. It is found that, although of the addition of Nb to partly replace Ta is benefit to the improvement of the GFA of the Ti-Zr-Ta-Si alloys and to reduce their costs, it is hard to obtain the fully amorphous alloys of Ti60Zr10Si15Ta15-xNbx(x=0, 3, 7, 11 at. %) by the water-cooling copper suction casting. The results indicate that the microstructure of the as-cast alloys is composed of beta Ti with the precipation of the fine crystallization phases such as Ti2Zr、TiSi、Si3Ti2Zr.The fracture strength of the Ti60Zr10Si15Ta8Nb7 alloy reaches 2150 MPa; Moreover, the Ti60Zr10Si15Ta15-xNbx(x=0, 3, 7, 11 at. %) alloys show an excellent corrosion performance in phosphate buffer salt solution, and with the increase of Nb content, the corrosion resistance of the alloys increased. However, in comparison with the fully amorphous Ti60Zr10Ta15Si15 alloy,the crystalline alloy exhibits the declined corrosion resistant.(3) The bulk amorphous alloy of Ti60Zr10Ta15Si15 was prepared by powder metallurgical(PM) method. The amorphous powders of Ti60Zr10Ta15Si15 alloy were firstly made by ball milling method, and then sintered under high pressures. The results show that, the ball milling process parameters have a significant impact on the amorphization efficiency of Ti alloy powder, If the ratio of the mass of balls to powders is 1 to 2, rotation speed is 350 rpm, and the ration of the mass of powder to the dispersant is 0.2%, the time of ball milling is 60 hours,the amorphization efficiency is the best. Temperature and pressure have an important influence on the microstructure and mechanical properties of sintered materials.Ti60Zr10Ta15Si15 powders were sintered at the temperature of the supercooled liquid region(780 K) under high pressure, no crystallization occurred. But at higher crystallization temperature(820 K) sintering, there has been a marked crystallization of amorphous alloys.The higher sintering pressure(5 GPa) does not cause a significant crystallization of the powder, and makes the material more uniform distribution of holes, organize more dense,elastic modulus and fracture strength were improved, and better wear resistance, greater vickers hardness.(4) By adding the plastic pure titanium powders into the amorphous titanium alloy powder, the composites of titanium amorphous alloys reinforced by pure titanium particleswas prepared by using PM method through high pressure sintering. The results show that, the volume fraction of the pure titanium and sintering pressure holding time have important influence on the microstructure of amorphous matrix composites and room temperature compression performance. There is not new phase appeared during the process of sintering,the sintering process is mainly controlled by physical diffusion mechanism of two phases. The composite material has certain plasticity, the pressure holding time also has important influence on the microstructure and room temperature compression performance of the amorphous composites. Phase identification of sintering materials shows that, when the pressure holding time is increased to 120 min from 10 min, no new phase is formed. And the grain combines more closely, resulting in the better mechanics performance of the composites material. |
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