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The Site Preferences of Transition Elements and Their Synergistic Effects on the Bonding Strengthening and Structural Stability of γ′ -Ni 3 Al Precipitates in Ni-Based Superalloys: A First-Principles Investigation
Metallurgical and Materials Transactions A ( IF 2.2 ) Pub Date : 2021-04-03 , DOI: 10.1007/s11661-021-06222-8
Rasim Eriş , M. Vedat Akdeniz , Amdulla O. Mekhrabov

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.



中文翻译:

镍基高温合金中过渡元素的位置偏爱及其对γ'-Ni3 Al沉淀物的结合强化和结构稳定性的协同效应:第一性原理研究

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(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(,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。

更新日期:2021-05-03
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