Precision Measurements of Gamma Coarsening at Low Volume Fractions in Nickel-Base Alloys

这一努力探讨了在含有低体积分数的析出物的金属合金中析出物粗化机制。析出相粗化机理及弹性应变效应是物理冶金领域亟待解决的重要问题。本研究选择了四种二元合金，以提供一系列晶格不匹配，从镍/硅体系的低0.003到镍/锗体系的高0.0112。考察了弹性相互作用和沉淀体积分数对颗粒粗化和平衡形状的影响。利用透射电子显微镜和磁分析技术跟踪了粗化动力学，从而可以测量粗化过程中富镍基体中的溶质浓度。磁控溅射是一种可以精确控制合金成分和均匀性的方法。本研究与高温金属合金的显微组织形成和稳定性有关。重点是二元镍基合金，这是高温合金成分发展的主要基础。

This effort explores mechanisms of precipitate coarsening in metal alloys that contain low volume fractions of precipitates. The mechanisms of precipitate coarsening and associated effects of elastic strain are important areas in physical metallurgy that needs to be resolved. Four binary alloys have been selected for this study to provide a range of lattice mismatches, from a low of 0.003 in the nickel/silicon system to a high of 0.0112 in the nickel/germanium system. The effects of elastic interaction and volume fraction of precipitate on particle coarsening and equilibrium shape are examined. The kinetics of coarsening are followed using the techniques of transmission electron microscopy and magnetic analysis, which enables measurement of the solute concentration in the Ni-rich matrix during coarsening. Magnetron sputtering is explored as a means of preparing alloys of precisely controlled compositions and homogeneity. %%% This research has relevance to microstructural formation and stability in high temperature metal alloys. The emphasis is on binary nickel-base alloys, the principal base for superalloy compositions development.