Construction of a New Method for the Design of Transition-metal-based Alloys with the Aid of a d-electrons Theory

提出了一种利用d电子理论设计过渡金属基合金的新方法。通过dv - x - α分子轨道计算，理论上得到了两个合金参数。一个是键序（Bo），它是原子间共价键强度的量度；另一个是d轨道能级（Md），它与元素的电负性和原子半径有关。本研究研究的合金有Ni-， Fe-, Zr， - Nb-和mo -基合金，这些合金在高温结构应用中都很重要。所得结果总结如下：(1)镍基合金：新引入了“合金矢量”的概念，用于预测合金中γ相的化学成分和体积分数。在这里，合金矢量由两个合金参数Md和Bo严格定义。在合金矢量的基础上，成功地设计了一些用于喷气发动机和发电厂的高温合金。(2)铁基合金：发现可以用Md-Bo图预测合金的相稳定性。利用Bo参数预测了铁素体合金的高温性能。基于这些结果，设计了电厂汽轮机和锅炉用铁素体合金。新的奥氏体合金也被设计用于第一个增殖反应堆。(3) Zr、Nb和mo基合金：通过实验数据和电子计算，得出了核电厂设计的一些指导原则。

A new method was proposed for the design of transition-metal-based alloys with the aid of a d-electrons theory. Two alloying parameters were obtained theoretically by the DV-Xalpha molecular orbital calculation. One is the bond order (Bo) that is a measure of the covalent bond strength between atoms and the other is the d-orbital energy level (Md) that is related to the electronegativity and atomic radius of elements. The alloys studied in this research were Ni-, Fe-, Zr, - Nb- and Mo-based alloys, all of which are important for high-temperature structural applications. The results obtained are summarize as follows ;(1) Ni-based alloys : A concept of "alloying vector" was newly introduced and used for the prediction of both the chemical composition and the volume fraction of the gamma phase in alloys. Here, the alloying vector is strictly defined by using the two alloying parameters, Md and Bo. On the basis of the alloying vectors, some superalloys for jet engines and electric power plants were designed successfully. (2) Fe-based alloys : It was found that the phase stability of the alloys could be predicted using a Md-Bo diagram. Also, high temperature properties in ferritic alloys were predicted using the Bo parameter. Based on these results, ferritic alloys were designed for turbines and boilers in electric power plants. New austenitic alloys were also designed for the first breeder reactors. (3) Zr-, Nb- and Mo-based alloys : From the experimental data and the electronic calculations, some guiding principles were obtained for the design of nuclear power plants.