Mechanisms And Modeling Of High-Temperature Anisotropic Deformation Of Single Crystal Superalloys

材料研究部授予新墨西哥州采矿与技术研究所的这一奖项是为了对高温合金进行研究，以提高其高温能力，从而实现更高效率的涡轮发动机。还需要改进寿命预测方法，以考虑微观结构的长期稳定性。这项研究的总体目标是了解和模拟单晶镍基高温合金的各向异性变形行为，单晶镍基高温合金含有高体积分数的伽马素析出物，并以相干方式嵌入在无序的伽马矩阵中。这些纳米结构材料表现出优异的高温性能。关于这些合金的内应力演化和位错运动机制，以及它们对蠕变响应和组织稳定性的影响，存在着相当大的争论。与洛斯阿拉莫斯中子科学中心合作进行的原位中子衍射研究是探索定向凝固技术获得的单晶和柱状晶合金的伽马和伽马主相的内部弹性应变状态。这种直接测量应该有助于证实或否定先前关于变形机制的假设。实验工作将与使用晶体塑性和有限元方法建模的力学响应建模相补充。纳米尺度的伽马需要位错和有限元分析相结合，而晶体塑性方法似乎是实现这些目标的有效手段。位错的运动及其流动阻力被考虑在用户定义的材料子程序的晶体塑性分量中；因此，可以结合不同类型的位错相互作用和速度定律。用户子程序的另一个重要组成部分是通过应变梯度塑性计算几何必要位错(GND)。这些位错可以解释观察到的界面位错网络，初步分析表明，应变梯度效应与一些与在这些合金中观察到的“漂流”组织有关的观察结果直接一致。该提议的主要智力价值是正在开发的用于探测纳米级内部应力的新实验技术和有限元建模研究的组合，其中包括晶体塑性和几何上必要的位错的演化。可以对应变率以及驱动漂流动力学的内能变化进行预测。该计划将在以下方面产生更广泛的影响。在科学层面，该方法将形成一个理解纳米相结构的框架，在纳米相结构中，约束变形需要结合几何上必要的位错，并且微观结构稳定性可能是一个重要的问题。在工业层面，与Research Applications Inc.的合作将有助于将建模方法插入涡轮机行业。此外，与Cannon Muskegon(合金开发商)和Pratt&amp；Whitney(飞机发动机制造商)的积极互动将直接使材料用户和供应商受益。最后，在教育层面，该项目的研究生和本科生将直接与行业和国家实验室互动，为他们在科学和技术领域的职业生涯做好准备。该州现有的基础设施计划将促进纳米材料研究以及大学和国家实验室之间的合作。

This award by the Division of Materials Research to New Mexico Institute of Mining and Technology is to carry out research on superalloys driven by the desire to increase their high temperature capability thereby enabling higher efficiency turbine engines. There is also a need for improved life prediction methodology that considers long-term microstructural stability. The overall goal of this research is to understand and model the anisotropic deformation behavior of single crystal nickel-base superalloys that contain a high volume fraction of gamma prime precipitates embedded coherently in the disordered gamma matrix. These nanostructured materials exhibit excellent high temperature properties. There is considerable debate regarding the evolution of internal stresses and mechanisms of dislocation movement, and their influence on the creep response and microstructural stability of these alloys. In-situ neutron diffraction studies to be carried out in collaboration with Los Alamos Neutron Science Center is to probe the internal elastic strain state in the gamma and gamma prime phases of single crystal and columnar grain alloys obtained by directional solidification techniques. Such direct measurements should help confirm or reject previous hypotheses on deformation mechanisms. The experimental work will be complemented with modeling of the mechanical response using crystal plasticity and finite element method modeling (FEM). The nanoscale dimensions of the gamma require a combination of dislocation and FEM analysis, and the crystal plasticity method appears to be an efficient means to achieve these objectives. The motion of dislocations and their resistance to flow is accounted for in the crystal plasticity component of a user-defined material subroutine; thus, different types of dislocation interactions and velocity laws can be incorporated. Another important component of the user subroutine is the accounting of geometrically necessary dislocations (GND) through strain gradient plasticity. These dislocations can account for the observed interface dislocation networks, and preliminary analysis shows that the strain gradient effect is in direct agreement with a number of observations related to a "rafting" microstructure observed in these alloys. The major intellectual merit of the proposal is a combination of novel experimental techniques being developed to probe internal stresses at the nanoscale level, and finite element modeling studies that include crystal plasticity and evolution of geometrically necessary dislocations. Prediction can be made about strain rates as well as changes in internal energy that drives the kinetics of rafting. The broader impact of the program will be in the following areas. At the scientific level, the methodology will form a framework to understand nanophase structures, where constrained deformation requires the incorporation of geometrically necessary dislocations, and where microstructural stability can be an important issue. At the industrial level, the collaboration with Research Applications Inc. will aid insertion of the modeling methodology into the turbine industry. In addition, active interaction with Cannon Muskegon (alloy developer) and Pratt & Whitney (aircraft engine manufacturer) will directly benefit both material users and suppliers. Finally, at the educational level, both graduate and undergraduate students in the program will interact directly with industry and the national laboratory and prepare them for careers in science and technology. The infrastructure program in place in the state will foster nanomaterials research and collaboration among the universities and the national laboratories.