Nb和Cr双掺杂γ-TiAl基合金的结构和延性研究

Investigations on the structures and ductibilities of γ-TiAl co-doped with Nb and Cr-substitution

γ-TiAl基合金是一种轻质耐高温材料,具有广阔的应用前景。采用基于密度泛函理论的第一性原理方法,计算了Nb或Cr单替位掺杂、Nb和Cr双替位掺杂γ-TiAl形成的合金体系的几何结构、原子平均形成能、布居数、电荷分布和弹性常数等。通过对形成能的计算分析,揭示Nb始终倾向于替代Ti原子,Cr的替代趋向则不明显。4个双掺杂体系均具有负的形成能,显示其结构的稳定性和易于实验制备的优势。通过晶胞轴比、弹性模量比和布居数计算与分析,发现Nb和Cr双掺杂对于改善合金体系的延性具有重要作用,预测Ti7NbAl7Cr和Ti7CrAl7Nb体系对于改善延性有较好的综合效果,且前者更为突出,揭示了实验探索的方向。

γ-TiAl based alloys are lightweight and withstanding high temperature materials with a broad application areas.Theγ-TiAl based alloys systems doped with Nb or Cr mono-substituting,Nb and Cr co-substituting are investigated by using first-principles method base on the density functional theory(DFT).The geometric structures,average formation energies of atom,populations,charges and elastic constants are calculated and analyzed with this method.The obtained formation energies of atom show that Nb atoms tend to substitute Ti atoms,while Cr atoms have no evident tendency.The four Nb and Cr co-doping systems possess negative formation energies indicating the stabilities of their structures and the advantages for experiment preparation.Through the calculations and analysis about axis ratios of unit cell,elastic modulus ratios and populations,the important effects of Nb and Cr co-doping for improving the ductility are presented.The paper forecasts that Ti7NbAl7 Cr and Ti7CrAl7 Nb systems possess good composite effect for the improvement of ductility,and the former was better than the latter.These results suggest the direction of experiment investigation.