物理化学学报 >> 2014, Vol. 30 >> Issue (2): 289-296.doi: 10.3866/PKU.WHXB201312191

理论与计算化学 上一篇    下一篇

Ti, Cr, Al和B合金化元素对α-Nb5Si3力学性能和电子结构的影响

邹爱华, 徐江, 黄豪杰   

  1. 南京航空航天大学材料科学与技术学院, 南京210016
  • 收稿日期:2013-09-25 修回日期:2013-12-19 发布日期:2014-01-23
  • 通讯作者: 徐江 E-mail:xujiang73@nuaa.edu.cn
  • 基金资助:

    国家自然科学基金(51374130)和航空科学基金(2013ZE52058)资助项目

Effects of the Alloying Elements Ti, Cr, Al and B on the Mechanical Properties and Electronic Structure of α-Nb5Si3

ZOU Ai-Hua, XU Jiang, HUANG Hao-Jie   

  1. School of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, P. R. China
  • Received:2013-09-25 Revised:2013-12-19 Published:2014-01-23
  • Contact: XU Jiang E-mail:xujiang73@nuaa.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (51374130) and Aeronautical Science Foundation of China (2013ZE52058).

摘要:

采用基于密度泛函理论(DFT)的第一性原理方法,通过比较形成能(Eform)、价电子浓度(VEC)、弹性常数(Cij)、剪切模量(G)与体模量(B)的比值(G/B)以及派-纳力(τP-N)等参量的变化,研究了Ti、Cr、Al和B合金化对D81结构的α-Nb5Si3结构稳定性和力学性能的影响. 研究表明:合金化元素Ti、Cr、Al和B分别优先占据α-Nb5Si3中Nb4c、Nb4c、Si4a和Si8h位置;添加不同含量合金化元素的α-Nb5Si3仍保持稳定的D81结构;Ti、Al和B合金化使α-Nb5Si3的脆性增加,而随着Cr含量的增加,α-Nb5Si3的韧性逐渐增强. 此外,态密度(DOS)和Mulliken布居等电子结构的计算结果表明:Ti、Al和B合金化导致α-Nb5Si3脆性增加的主要原因是提高了共价键的强度;而Cr合金化的增韧作用主要来源于共价键数量的减少和强度的削弱,以及更多的反键态被占据.

关键词: 第一性原理, 铌硅化合物, 结构稳定性, 韧/脆性, 电子结构

Abstract:

The structural stability and mechanical properties of α-Nb5Si3 alloyed with Ti, Cr, Al and B were investigated using first- principles methods based on density functional theory (DFT) by comparing the formation energy, valence electron concentrations, elastic constants, the shear modulus/bulk modulus ratio, and the Peierls stress. The results show that the structures of the α-Nb5Si3 alloys retain the stable D81 structure, in which the alloying elements Ti, Cr, Al and B prefer to occupy the Nb4c, Nb4c, Si4a and Si8h sites of α-Nb5Si3, respectively. The addition of Ti, Al and B increase the brittleness of D81 structured α-Nb5Si3, while Cr addition is beneficial to the toughness of α-Nb5Si3. Moreover, the influence of the alloying elements on the ductility/brittleness of α-Nb5Si3 was investigated based on analysis of the electronic structure, density of states and Mulliken population. The increased brittleness of α-Nb5Si3 by the addition of Ti, Al and B can be attributed to enhanced orientation of the covalent bonds, whereas Cr addition weakens the number and strength of covalent bonds and more anti-bonding states are occupied, thus improving the toughness.

Key words: First-principles, Niobium-silicon compound, Structural stability, Ductile/brittle behavior, Electronic structure

MSC2000: 

  • O641