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

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

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.