Effect of Nb Addition on Young's Modulus and Linear Expansion Coefficient of Cast Pure Titanium

摘要

In order to develop a material with low elastic modulus for medical implantation or with low linear expansion coefficient for aerospace, five kinds of Ti-Nb alloys (Nb=15 %, 20 %, 25 %, 30 %, 35 %, by weight) were prepared and solution-treated in the present study to investigate the effect of single Nb addition on the Young's modulus and linear expansion coefficient of cast pure titanium. The results showed that element Nb can significantly decrease the elastic modulus and linear expansion coefficient of cast pure titanium. In the range of 15wt.% to 35wt.% Nb addition, the Ti-20wt.%Nb alloy has the lowest Young's modulus (E=56 GPa), with a decrease of about 46.7 % compared with that of pure titanium (105 GPa); the Ti-25wt.%Nb alloy has the lowest linear expansion coefficient (α=6.6×10~(-6)/°C, from 20 to 100 °C), with a decrease of about 17.5 % compared with that of pure titanium (8.0×10~(-6)/°C). In addition, the microstructure observation and measurements of mechanical properties were also performed. The results indicated that the microstructures of the solution-treated Ti-Nb alloys are all composed of matrix β-phase and acicular precipitated phases α' and α", and the α" phase and β-phase are the main reasons of low Young's modulus and low linear expansion coefficient for the Ti- Nb alloys. The tensile strength and elongation of the Ti-Nb alloys are in the range of 520 to 660 MPa and 19 % to 32 %, respectively.