4d过渡金属替位掺杂γ-TiAl基合金的第一性原理研究

First-principles Investigation on γ-TiAl Based Alloys Substitutively Doped with 4d Transition Metals

采用基于密度泛函理论的第一性原理方法,计算研究了4d过渡金属X在γ-TiAl中替位掺杂形成的Ti7XAl8和Ti8Al7X体系的几何结构、总能量和弹性常数。对系统总能量、形成能的计算结果揭示Tc、Ru、Mo和Nb替代Al原子(或Ti原子),Rh和Pd替代Al原子掺杂体系比纯γ-TiAl体系更稳定,有利于制备γ-TiAl基合金。分析Ti7XAl8和Ti8Al7X体系的轴比c/a发现,4d过渡金属元素Y、Zr、Tc、Ru、Rh、Mo和Nb替代Al,Y、Ag、Rh和Pd替代Ti均能明显改善γ-TiAl基合金的延性。对弹性模量比的研究表明,Y、Zr、Tc、Ag、Ru、Rh、Pd、Mo和Nb替代Al原子掺杂有利于改善γ-TiAl基合金的韧性。综合分析确认,Mo和Nb易于添加到γ-TiAl基合金中并且有利于改善材料的延性和韧性。这一结论能够与他人的实验研究结果相互佐证。

Ti7 XAl8 and Ti8 Al7 X systems formed by substitutive doping of 4d transition metals in γ-TiAl were investigated by first-principles method based on density functional theory.The geometry structures,total energies and elastic constants of these systems were calculated and analyzed.The obtained total energies and formation energies of the systems show that the crystals doped with Tc,Ru,Mo and Nb substituting Al（or Ti）,and doped with Rh and Pd substituting Al are more stable than pure γ-TiAl system.This is beneficial to the preparation of γ-TiAl based alloys.The analysis about the axial ratios of Ti8 Al7 X and Ti7 XAl8 systems indicates that 4d transition metal element Y,Zr,Tc,Ru,Rh,Mo,Nb substituting Al,and Y,Ag,Rh,Pd substituting Ti can distinctly improve the ductility of γ-TiAl based alloys.The results of elastic modulus ratios exhibit that Y,Zr,Tc,Ag,Ru,Rh,Pd,Mo and Nb substitutions for Al are propitious to improve the toughness of γ-TiAl based alloys.Comprehensively,Mo and Nb are easy to be planted into γ-TiAl alloys and are helpful for the improvement of the material toughness.This conclusion and the experimental results reported in literature can be validated with each other.