医用低模量Ti-Mo-Sn合金的第一性原理计算研究

First-principles calculations study of low Young’s modulus Ti-Mo-Sn alloys for biomedical applications

摘要:

本文采用基于密度泛函理论的第一性原理计算方法,研究了Mo含量对Ti-xMo-Sn(x = 1-5)合金相稳定性、弹性性质及其电子结构的影响,采用Voigt-Reuss-Hill近似方法估算了体系的多晶弹性模量,提出了低模量Ti-Mo-Sn合金的价电子准则,为医用钛合金的设计提供了理论基础。研究结果表明：Mo元素合金化能明显提高Ti-Mo-Sn合金的β相稳定性,所有合金都满足力学稳定性要求,随Mo元素含量增加,合金的体积模量B逐渐变大,而剪切模量G和杨氏模量E先减小后增大,其中 Ti-3Mo-Sn具有最低的杨氏模量(48.47 GPa)和最佳的延展性,在生物医用领域展现出巨大潜力。Ti-xMo-Sn合金的弹性各向异性A与Mo元素含量有关,低弹性模量始终沿<100>晶体学方向。最后,结合Ti合金的总态密度(DOS)和分波态密度(PDOS)分析讨论了Mo元素对β相结构稳定性的影响机制。

Abstract:

In the present study, the Density Functional Theory (DFT) implemented in Vienna Ab-initio Simulation Package(VASP) code was employed to investigate the β phase stability and elastic properties of Ti-xMo-Sn (x=1-5) alloys. The structural properties were investigated after geometrical optimization. The general elastic properties (such as bulk modulus B, shear modulus G, Young"s modulus E) were estimated by Voigt-Reuss-Hill approximation. In addition, the valence electron criterion for design of low Young"s modulus Ti-xMo-Sn alloys was proposed. The calculated cohesive energy indicate that Mo can increase the β phase stability of Ti-xMo-Sn alloys. The Pugh ratio B/G and Poisson"s ratio ν suggest that all these alloys exhibit ductile properties. For Ti-xMo-Sn alloys, the smaller tetragonal shear constant C′ may induce the lower Young’s modulus. Ti-3Mo-Sn possess the lowest Young’s modulus (48.47 GPa) and best ductility, showing great potential for biomedical applications. The elastic anisotropy A of Ti-xMo-Sn alloys is sensitive to Mo concentration, the lowest Young’s modulus always oriented in the <100> crystallographic direction. In the end, detailed analysis of total and partial DOS explained the calculated results.