Coarsening and growth of meta-stable gamma''-precipitates in Nickel-base Superalloys

该项目的目的是研究相场模拟方法，以模拟镍基模型合金中的伽马析出，辅以各自的实验特征。中心目标是研究相场模拟方法对选定加载条件下的伽马析出生长和随后的粗化动力学的预测能力。相场预测的实验参考将是本项目中产生的高质量的实验组织数据。在相应的实验研究中，我们计划对一系列不同的样品，在选定的载荷下，在不同的时间时效，覆盖从初始沉淀长大到伽马‘’粗化过程的整个时间范围，定量测量伽马‘’粒子的尺寸和形状。该项目的主要目标是仅从实验上研究伽马‘’粒子的沉淀硬化机制，这对于理解高温镍基变形合金(如IN718)的硬度具有很高的基础意义。与伽马‘-粒子相反，伽马’-沉淀物以三种不同的取向变化存在，导致在载荷下的粗化行为相当复杂。伽马粒子生长和随后粗化背后的基本物理机制涉及材料溶液化学和微观相结构的热力学之间的强烈耦合。根据优先方案的目标，该项目的一个科学关键目标是推动相场建模作为一种技术，在微观水平上解决这种热-化学-机械相互作用，从而在冶金和材料科学背景下实现更好的实用可用性。

The aim of the project is to study phase field modelling approaches for the simulation of gamma''- precipitation in a Ni-base model alloy, assisted by respective experimental characterisations.The central goal is to investigate the predictive power of the phase field modelling approache with respect to the kinetics of gamma''- precipitation growthas well as subsequent coarsening under selected loading conditions.The experimental reference for the phase field predictions will be high quality experimental microstructure data, generated within the project. In corresponding experimental investigations, we plan to quantitatively measure the sizes and shapes of the gamma''- particles for a series of different samples, aged under selected loadings at different times, covering the whole time range from the initial precipitation growth right into the gamma''- coarsening regime.A primary goal of the project is to experimentally investigate the mechanism of precipitation hardening of gamma''- particles only, which is of high fundamental relevance for the understanding of the hardness in high temperature Ni-base wrought alloys such as IN718. In contrast to gamma'- particles, the gamma''- precipitates exist in three different orientational variants, leading to a quite complex coarsening behaviour under load. The elementary physical mechanisms behind the growth and subsequent coarsening of gamma''- particles involve a strong coupling between the materials solutal-chemistry and the thermo-mechanics of the microscopic phase structure.According to the goals of the Priority Programme, it is a scientific key goal of the project to push forward phase field modelling as a technique, which resolves this thermo-chemo-mechanic interplay on a microcopic level, towards a better practical usability in a metallurgical and materials scientific context.