Coarsening Kinetics, Coherent Equilibrium and Evolution of Morphology and Spatial Correlations in Nickel-Base Gamma/ Gamma' Alloys

在本研究的过程中，探索了二元Ni-X合金中γ素数型析出相（Ni3X, X = Al, Ga， Ge或Si）粗化的几个新方面。这些包括：(1)进一步研究小体积分数下的异常粗化动力学，fv；(2)定量表征了fv较小时γ素体析出的凹立方形态的演变，以及最终导致镍基γ / γ素体合金中漂流的空间相关性；(3)低温（t550℃）下γ素粗化的磁分析研究，定量测量了相干应变和fv对Ni-X合金（包括Ni-Ti合金）平衡相干溶解度极限的影响。并提出了在二元Al-Sc合金中开展Al3Sc析出物粗化动力学研究的新课题。主要的分析方法是暗场透射电子显微镜（TEM），应用于扫描TEM底片的图像分析软件，测量ni基合金γ′粗化过程中基体溶质浓度变化的磁分析，以及对Al-Sc合金进行可比测量的电阻率。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，这是高温合金发展的主要基础。＊＊＊

9526238 Ardell Several new aspects of the coarsening of gamma prime type precipitates (Ni3X, X = Al, Ga, Ge or Si) in binary Ni-X alloys are pursued during the course of this research. These include: (1) further studies of anomalous coarsening kinetics at small volume fractions, fv; (2) quantitative characterization of the evolution of the concave cuboidal morphology that gamma prime precipitates attain when fv is small, and characterization of the spatial correlations that eventually lead to rafting in nickel-base gamma/gamma prime alloys; (3) investigations of gamma prime coarsening at lower temperatures (T 550 C) using magnetic analysis to measure quantitatively the influence of coherency strains and fv on the equilibrium coherent solubility limits in Ni-X alloys, including Ni-Ti alloys. It is also proposed to initiate a new project on the coarsening kinetics of Al3Sc precipitates in binary Al-Sc alloys. The principal methods of analysis are dark-field transmission electron microscopy (TEM), image-analyzing software applied to scanned TEM negatives, magnetic analysis to measure the variation of the solute concentration of the matrix during gamma prime coarsening in Ni-base alloys, and electrical resistivity to make comparable measurements in Al-Sc alloys. %%% This research has relevance to microstructural formation and stability in high temperature metallic alloys. The emphasis is on binary nickel-base alloys, the principal base for superalloy development. ***