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本文采用Ti,Cr,Al,Hf元素对金属间化合物β-Nb5Si3进行了合金化,利用基于平面波赝势理论的第一原理方法对其能量、电子结构、晶体常数、弹性常数进行了计算。合金化前后的能量变化表明:Ti,Cr,Hf元素优先替换NbI, NbI, NbII的Nb原子,而Al使得β-Nb5Si3 稳定性降低。合金化原子的占位使得β-Nb5Si3的晶体参数发生变化,其中:Ti、Cr原子能够降低晶胞的c/a值,而Hf促使晶胞从四方晶系向正交晶系转变。态密度计算表明 Ti,Cr,Hf提高了β-Nb5Si3相的导电性。采用Voigt公式计算掺杂前后各体系的弹性模量;并基于Pugh经验公式,对合金的室温韧性进行了评价,结果表明:Ti,Cr元素的掺杂降低了β-Nb5Si3相的室温断裂韧性,而Hf元素的掺杂能够提高β-Nb5Si3的断裂韧性。
In this paper, the intermetallic compound β-Nb5Si3 has been alloyed with Ti, Cr, Al and Hf elements. The energy, electron structure, crystal constants and elastic constants have been calculated by the first principle method based on the plane wave pseudo-potential theory. The energy changes before and after alloying show that Ti, Cr and Hf elements preferentially replace the Nb atoms of NbI, NbI and NbII, while Al makes the stability of β-Nb5Si3 lower. The alloying atoms occupy the positions of the β-Nb5Si3 crystals, in which Ti and Cr atoms reduce the c / a value of the unit cell, and Hf promotes the transformation of the unit cell from the tetragonal system to the orthorhombic system. State density calculations show that Ti, Cr and Hf improve the conductivity of β-Nb5Si3 phase. The Voigt formula was used to calculate the elastic modulus of each system before and after doping. Based on the Pugh empirical formula, the room temperature toughness of the alloy was evaluated. The results showed that the doping of Ti and Cr reduced the room temperature fracture toughness of β-Nb5Si3 phase, The Hf element doping can improve the fracture toughness of β-Nb5Si3.