Ru对NiAl[100](010)刃型位错电子结构的影响

Effect of Ru on the Electronic Structure of the [100](010)Edge Dislocation in NiAl

利用DMol和离散变分法,研究了Ru在NiAl [100](010)刃型位错中择优占位和合金化效应。杂质偏聚能的计算结果表明,Ru会优先占据Al心位错芯中的Al格位。原子间相互作用能、电荷密度和态密度的分析表明,杂质原子和相邻基体原子之间形成了较强的化学键,使Ru原子与位错芯区近邻基体原子间因强相互作用形成一个整体。此外,在掺杂体系中,穿过滑移面的基体原子间相互作用减弱,而沿滑移方向基体原子间的相互作用加强。这样的成键特性有利于位错线沿滑移面的移动形成扭折,扭折的成核及迁移促使位错运动,从而改善NiAl合金的韧性。

NiAl intermetallics have potential application in the aerospace industry as a new high temperature structure material due to its high melting temperature, good thermal conductivity, low density,and good oxidation resistance. However, possible technological applications of NiAl are limited by its poor ductility at low temperatures and brittle grain boundary fracture at elevated temperature. Different methods have been dedicated to manage the brittle behavior of NiAl. Micro-alloying is a effective method.Dislocation is a complicated and widely existing crystal defect. The interaction between dislocation and impurity can greatly influence the mechanical properties of materials. However, the mechanism of interaction between the dislocation and alloying element is not clear. In the work, using the DMol and the discrete variational method within the framework of density functional theory, the site preference and alloying effect of Ru in the [100](010) edge dislocation core(DC) of NiAl are studied. The results of the impurity formation energy show that Ru exhibits a strong Al site preference. The analyses of the interatomic energy, the charge distribution and the partial density of states show that the strong bonding states are formed between the impurity atom and neighboring host atoms. Meanwhile, the bonds keep the atoms in the DC as a whole, which will benefit formation of kink. In addition, in the doped DC system, the interactions between the pair of atoms across the slip plane are weaker, while along the slip direction the interactions are stronger than those in the clean DC system. This bond characters may be in favor of the motion of [100](010) edge dislocation, which will improve the ductility of NiAl.