| Titanium and titanium alloys are a new kind of bio-medical metal materials after these such as stainless steel, cobalt-base alloys and precious metals.Titanium and titanium alloys with high strength, high toughness, low elastic modulus, corrosion resistance, wear resistance and excellent bio-compatibility become the first choice of medical implant products.This paper has the aid of clusters model theory, namely CN14 coordination polyhedron as basic structure model of clusters, then makes the clusters alloying properly. According to the mixing enthalpy of the alloy elements Nb、Sn、Zr and Ti, SnTi14 clusters can be set up with Sn as the center atom, Ti as the shell atom. We choose three Nb as connection atoms, then the component formula of basic clusters model is [SnTi14]Nb3, meanwhile the electron concentration (e/a) is 4.167, the molybdenum equivalent is 7.9 of the designed titanium alloy.Because of Ti and Zr with similar chemical characteristics, we can replace Ti on the shell part of clusters by Zr, after that the mixing enthalpy between Zr and Nb is more positive meaning that the Zr alloying can weaken binding force between the connection atoms Nb and (Ti, Zr) on cluster shell, which decreases the connection intensity between clusters, and that is expected to reduce the overall elastic modulus. At the same time, the mixture enthalpy of Zr and Sn as clusters center atoms more negative(△ HSn-Zr=-43kJ/mol),the binding force in clusters is stronger and more stable in favour of obtaining stable β phase structure.Four alloy ingots Ti-26Nb-11 Sn、Ti-25.6Nb-10.8Sn-4.2Zr、Ti-25.1Nb-10.7Sn-8.2Zr、 Ti-24.6Nb-10.4Sn-12Zr were melted with vacuum arc furnace in this experiment. XRD phase analysis and micro-structure analysis were respectively carried out on as-cast alloys and homogenizing treatment alloys. The results show that the designed alloys in as-cast and homogenizing treatment are a single β phase, satisfying the requirement of design theory.Hardness test was carried out on the homogenizing treatment alloys,the result indicates that with the increase of Zr content, solid solution strengthening effect appears more obvious and then alloy hardness value increase more, the highest hardness value reaches 302.8HV0.2. And then compression mechanical properties test was carried out on homogenizing treatment alloys,the result finds that four alloys have good plasticity and elastic modulus values reduce with the increase of Zr content. This is because the content of Zr is more, connection strength between clusters is weaker and the modulus of elasticity is lower.The experimental result shows that the lowest compression elastic modulus value is 9.08 GPa. Electrode polarization curve measurement was carried on homogenizing treatment alloys,the result finds that titanium alloy with the composition of Ti-25.1Nb-10.7Sn-8.2Zr has the best corrosion resistance.According to the comprehensive analysis of mechanical properties and corrosion resistance on the four composition of titanium alloy in the whole paper,it can be summarized that Ti-25.1Nb-10.7Sn-8.2Zr is more satisfied with the design requirements of β titanium alloys of bio-medical and low elasticity than the other three composition. |
PDF Full Text Request