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

摘要

The structural stability and mechanical properties ofα-Nb5Si3 al oyed 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 theα-Nb5Si3 al oys retain the stable D81 structure, in which the al oying elements Ti, Cr, Al and B prefer to occupy the Nb4c, Nb4c, Si4a and Si8h sites ofα-Nb5Si3, respectively. The addition of Ti, Al and B increase the brittleness of D81 structuredα-Nb5Si3, while Cr addition is beneficial to the toughness ofα-Nb5Si3. Moreover, the influence of the al oying elements on the ductility/brittleness ofα-Nb5Si3 was investigated based on analysis of the electronic structure, density of states and Mul iken population. The increased brittleness ofα-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.%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Mul iken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。