Atomistic Studies of Concentrated Multicomponent Nickel-Based Alloys Utilizing Atom-Probe Tomography and Vacancy-Mediated Lattice Kinetic Monte Carlo Simulations

本研究项目的重点是镍铝基合金中的相分离是如何发生的，镍铝基合金是所有镍基高温合金的物理基础，它可能包含多达12种不同的合金元素，每种元素都有特定的用途。镍基高温合金用于涡轮叶片和磁盘，它们是军用和商用喷气发动机以及发电的天然气涡轮发动机的核心，并且在极高的温度下运行。为了在这种技术上重要的合金类别中在原子尺度上研究这些材料，西北大学原子探针断层扫描中心将广泛利用这些材料。原子探针层析成像是一种独特的技术，可以在亚纳米到纳米尺度上表征材料。将该技术应用于镍铝基合金，将有助于了解最终微观组织的发展，这对于在微观和宏观长度尺度上控制材料的物理力学性能具有重要的意义和技术意义。这项工作将有助于培养下一代的材料科学家在这种最先进的技术状态。摘要浓多组分镍基过饱和固溶体在合金相分离的不同阶段（成核、长大和粗化）的动力学路径是了解最终微观组织发展的关键，对于在微观和宏观长度尺度上控制材料的物理力学性能具有重要的意义和技术意义。为了研究相分离的时间演化，PI将利用紫外激光辅助原子探针断层扫描（APT）和空位介导的晶格动力学蒙特卡罗（LKMC）模拟进行相关实验，从而可以在原子尺度上理解这种演化。这项工作还将采用显微硬度测量和透射电子显微镜实验。从原子聚集形成具有短程有序（SRO）的胚胎开始研究时间演化，这是稳定核（沉淀）的前体；因此，可以研究SRO，然后以长程序（LRO）析出并观察生长和粗化。用于描述时间演变的所有10多个物理参数均通过APT测量并通过LKMC模拟进行模拟。此外，PI将研究准稳定粗化过程中的演变，并将这些结果与选定的三元和四元镍基合金的Philippe-Voorhees （P-V）多组分合金平均场模型（2013年）进行比较，该模型涉及使用热力学和迁移率数据库。这将产生一种现实的方法来准平稳粗化嵌入在基体中的沉淀的多分散分布。这种多管齐下的实验和模拟方法通过连续体长度尺度在原子尺度上获得信息。

Non-Technical AbstractThis research program is focused on how phase separation occurs in nickel-aluminum based alloys, which are the physical bases of all nickel-based superalloys and which may contain up to 12 different alloying elements, with each element serving a particular purpose. Nickel-based superalloys are utilized for turbine blades and disks, which are at the heart of both military and commercial jet engines as well as natural gas-fired turbine engines that produce electricity, and which operate at extremely elevated temperatures. To study these materials at an atomic scale in this technologically important class of alloys, extensive utilization will be made of the Northwestern University Center for Atom-Probe Tomography. Atom-Probe Tomography is a unique technique that allows characterizing materials at the sub-nano to nanoscale. Applying this technique to nickel-aluminum based alloys will allow understanding the development of the final microstructure, which is of great significance and technological importance for controlling the physical and mechanical properties of a material at microscopic and macroscopic length scales. This work will help train the next generation of materials scientists in this state of the art technique. Technical AbstractThe kinetic pathways in the different stages of alloy phase separation (nucleation, growth and coarsening) of concentrated multicomponent nickel-based supersaturated solid-solutions are critical for understanding the development of the final microstructure, which is of great significance and technological importance for controlling the physical and mechanical properties of a material at microscopic and macroscopic length scales. To study the temporal evolution of phase separation, the PI will perform correlative experiments utilizing ultraviolet laser-assisted atom-probe tomography (APT) and vacancy-mediated lattice-kinetic Monte Carlo (LKMC) simulations, which permit understanding this evolution on an atomic scale. This work will also employ microhardness measurements and transmission electron microscopy experiments. The temporal evolution is studied starting with the clustering of atoms to form embryos exhibiting short-range order (SRO), which are the precursors of stable nuclei (precipitates); thus, allowing study of SRO and then precipitates with long-range order (LRO) and observation of growth and coarsening. All of the 10 plus physical parameters, for describing the temporal evolution, are measured via APT and simulated via LKMC simulations. Additionally, the PI will study the evolution during the quasi-steady coarsening regime and compare these results with the Philippe-Voorhees (P-V) mean-field modeling of multicomponent alloys (2013) for selected ternary and quaternary nickel-based alloys, which involves the use of both thermodynamic and mobility data bases. This will yield a realistic approach to quasi-stationary coarsening of a polydispersed distribution of precipitates embedded in a matrix. This multipronged experimental and simulation approach yields information at the atomic scale through the continuum length scale.