Advanced mechanical properties of Ni-based superalloys strongly depend on the site preferences of alloying X elements in γ′-Ni₃Al-X precipitates, which are associated with the partial bonding characteristics between Ni, Al, and X atoms. Therefore, in the current work, the site occupancy tendencies of transition X metals were revealed via first-principles ab initio calculations at 0 K. Bonding features of Ni-Al, Ni-X, and Al-X pairs were simulated by using the charge density difference (CDD), electron localization function (ELF), and density of states (DOS) methods, respectively. According to simulations, higher atomic size X elements preferably occupy Al sites of γ′-Ni₃Al-X intermetallics and lead to strong covalent-like directional bondings between themselves and their nearest neighbor (NN) Ni atoms along 〈110〉 directions. However, if these larger X metals substituted for Ni sites, the bonding properties would differ by plane due to the nature of the L1₂-type crystal structure of γ′-Ni₃Al-X precipitates. Considering all transition elements, refractory metals (i.e., X = Re, W, Mo, Ta, or Nb) appear as the most effective strength inducers, improving the structural stability of γ′ phase, even if Ni site substitution of X = Re atoms would start to increase structural instability. On the other hand, relatively small alloying X elements having electron configuration similarities with Ni (i.e., X = Co, Cu, Rh, Pd, Ag, Ir, Pt, or Au) are more likely to worsen bonding strengthening. Instead, these transition X metals creating metallic bondings with NN Ni atoms would contribute to ductility and malleability of Ni-based superalloys. Furthermore, depending on the relative atomic size of γ′-former and refractory elements, the phase and site preferences of refractory atoms would alter in multicomponent systems. As a result of the attractive or weak repulsive forces between Re-Re, Re-Mo, and Re-W pairs, the structural stability of the constituent phases would deteriorate and harmful topologically close-packed (TCP) phases would precipitate.

Ni基超合金的先进的机械性能很大程度上取决于合金在X元素的网站偏好γ' -Ni ₃的Al-X析出物，这是用Ni，Al和X的原子间的部分粘合特性相关联。因此，在当前工作中，通过第一性原理从头计算从零开始揭示了过渡X金属的位点占据趋势。通过使用电荷模拟了Ni-Al，Ni-X和Al-X对的键合特征密度差（CDD），电子定位功能（ELF）和状态密度（DOS）方法。根据模拟，较高原子大小X元素优选占据的Al位点γ' -Ni ₃Al-X金属间化合物会导致它们与它们的最近邻（NN）Ni原子之间沿<110>方向形成强共价键状的定向键。但是，如果取代位点的Ni这些较大的X金属，粘结性能将由平面由于L1的性质而有所不同₂的型晶体结构“γ -Ni ₃的Al-X的沉淀物。考虑到所有过渡元素，难熔金属（即X = Re，W，Mo，Ta或Nb）似乎是最有效的强度诱发剂，从而改善了γ'的结构稳定性即使X = Re原子的Ni位取代也会开始增加结构的不稳定性。另一方面，具有与Ni的电子构型相似性的相对较小的合金X元素（即，X ＝ Co，Cu，Rh，Pd，Ag，Ir，Pt或Au）更可能使键合强化变差。相反，这些过渡X金属与NN Ni原子形成金属键将有助于Ni基高温合金的延展性和延展性。此外，取决于γ'的相对原子尺寸-前体和耐火元素，在多组分系统中，耐火原子的相和位点偏好会发生变化。由于Re-Re，Re-Mo和Re-W对之间的吸引力排斥力或弱排斥力，组成相的结构稳定性将变差，并且有害的拓扑紧密堆积（TCP）相将沉淀。