Atomistic Study of the Interface Energy in Nickelbase Superalloys

涡轮机中使用的高温部件通常由镍基高温合金制成。这些合金的高强度是由于沉淀颗粒。由于锻造的是大型部件，因此在锻造过程中必须不存在强化颗粒，只有在较低的温度下才可能析出。锻造过程中必须存在其他沉淀物（含铍的δ相和含钛的η相），因为它们改善了合金的微观结构。因此，为了提高这些合金的使用温度，需要调整δ-和η-相的性能。δ-和η-相颗粒的析出取决于这些相与镍基体之间的界面能。这一建议的目的是计算这些和所谓的γ”相的界面能，并研究合金元素如何影响界面。这将提高对这些粒子的沉淀以及如何在更高温度下保持它们稳定的理解。原子模拟被用于实现这一目标。密度泛函理论方法允许计算任意原子构型的能量。然而，它仅限于几百个原子。此外，使用了所谓的经典分子动力学方法，可以模拟大量的原子。然而，这种方法需要经验参数作为输入，因此不能用于研究所有的合金元素。使用这两种方法可以研究界面能的不同方面。这些结果还将通过有限的实验研究得到证实。

High-temperature components as they are used in turbines are usually made of nickel-base superalloys. The high strength of these alloys is due to precipitated particles. Since large components are wrought, the strengthening particles must not be present during the forging process and may precipitate only at lower temperatures. Other precipitates (the niobium-containing delta and the titanium-containing eta-phase) have to be present during forging because they improve the microstructure of the alloy. To increase the service temperature of these alloys thus requires to adapt the properties of the delta- and eta-phase.The precipitation of particles of the delta- and eta-phase is determined by the interfacial energy between these phases and the nickel matrix. It is the aim of this proposal to calculate the interfacial energy of these and the so-called gamma"-phase and to investigate how alloying elements affect the interface. This will improve the understanding of the precipitation of these particles and how to keep them stable at higher temperatures.Atomistic simulations are used to achieve this goal. The density functional theory method allows to calculate the energy of arbitrary configurations of atoms. However, it is restricted to several hundred atoms. Additionally, the so-called classical molecular dynamics method is used that can simulate large numbers of atoms. This method, however, needs empirical parameters as input and thus cannot be used to investigate all alloying elements. Using both methods allows to study different aspects of the interfacial energy. The results will also be confirmed by a limited amount of experimental investigations.