Acta Phys. -Chim. Sin. ›› 2014, Vol. 30 ›› Issue (2): 289-296.doi: 10.3866/PKU.WHXB201312191

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

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).

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