Coarsening Kinetics and Morphological Evolution of Ni-X \(Solid Solution\) Precipitates in Ordered Ni3X Alloys \(X = Al, Ge, Ga\)

本项目的目的是利用广泛的电子显微镜和图像分析软件，更好地了解Ni-Al、Ni-Ga和Ni-Ge合金中无序析出相粗化动力学和形态演变的基本方面。还将研究固溶体析出相的居里温度，以确定析出相的成分在时效过程中是否发生变化。这将是第一次尝试研究沉淀反应过程中沉淀物自身成分的变化。拟议研究的最终目标是更好地了解影响镍基合金粗化动力学、形态和空间相关性的详细因素，这些因素在各种需要高温材料的结构技术中得到应用。这项研究的一个目的是获得定量的实验证据，证明Ni-Al和Ni-Ge析出物的粗化动力学较慢，据信是由这些原子物种更复杂的扩散引起的。除了目前所考虑的界面能和晶格失配外，还将探讨反相界面能在析出相形态演变中的可能作用。这项研究的资金为研究生提供了继续接触材料科学前沿研究的机会。这项研究发展了对沉淀粗化和形态的潜在原因和机制的新的和更好的理解。该研究将为开发性能优良的镍基合金做出重要贡献。

This project is aimed at a greater understanding of fundamental aspects of the coarsening kinetics and evolution of morphology of disordered precipitates in Ni-al, Ni-Ga and Ni-Ge alloys using extensive electron microscopy coupled with image-analysis software. The Curie temperatures of the solid-solution precipitate phase will also be investigated to determine whether the compositions of the precipitate phases change during aging. This will be the first time any attempts made to investigate the changes in the composition of precipitates themselves during a precipitation reaction. An ultimate objective of the proposed research is better understanding of the detailed factors affecting coarsening kinetics, morphology and spatial correlation in Ni-base alloys that find applications in varied technologies that require high temperature materials for the structures. An objective of the study is to obtain quantitative experimental evidence for the slower kinetics of coarseing of Ni-Al and Ni-Ge precipitates believed to arise from more complex diffusion of these atomic species. In addition to the interfacial energy and lattice mismatch that were considered so far, the possible role of antiphase boundary energy in the evolution of precipitate morphology will be explored. The funding for this research provides graduate researchers a continued exposure to research in the forefront of materials science.This research develops new and better understanding of the underlying reasons and mechanisms of precipitate coarsening and morphologies. The research will make significant contribution to the development of Ni-base alloys with optimum properties.