Ni基合金γ/γ'相界Ir合金化时结构特性的第一原理研究

First-Principles Study on the Structures and Properties of the γ/γ' Interface with Ir Addition in Ni-Base Single Crystal Superalloys

采用非相对论第一原理分子轨道DV-Xα模型簇方法,计算了Ni基单晶超合金γ/γ'相界的电子结构,并从键重替聚居数(QAB)、界面原子层间的部分键合强度,以及界面原子局域环境总键合强度几个方面,对Ir合金化前后γ/γ'界面的结构稳定性、脆化特性、相间断裂的难易程度等几个方面对γ/γ'相界的结构特性进行了分析。结果表明:Ir合金化能增强γ/γ'界面Ni-Ni与Ni-Al原子间的键合强度,价键强度的增加有如下的变化趋势:QNi-Ni<QNi-Al<OIr-Ni<QIr-Al,相界上,当被置换原子的种类与位置不同时,Ir合金化对γ/γ'相界结构性能的影响程度也不相同,比较而言,Ir置换γ相中的Ni最有利于提高γ/γ'相界的结构稳定性与相间抗断强度。

By using the discrete variational Xα(DV-Xα) method, the electronic and bonding structures of γ/γ' interfaces with and without Ir addition in Ni-base single crystal superalloys were calculated in the framework of the first-principles theory. Several bonding parameters such as the bond overlap population (QAB), the partial bonding strength of interlayer and the local environmental total bonding strength have been applied to characterize and analyze the structural stability and ductility of γ/γ' interfaces as well as the difficulty of fracture along γ/γ' interface. Result shows that Ir addition can improve bonding strengths of Ni-Ni and Ni-Al atom pairs in γ/γ' interfaces, and the bonding strength increase in the following order: QNi-Ni less than or equal QNi-Al less than or equal QIr-Ni less than or equal QIr-Al. With a difference in sorts and sites of atoms substituted by Ir in γ/γ' interface, a distinct different influence of Ir addition on the structures and properties of γ/γ' interfaces can be seen. As comparing, it is found Ir replacing Ni in the y phase is most beneficial to improve structural stability and strength against rupture along γ/γ' interface.