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

小行星9526238 在本研究过程中，对二元Ni-X合金中γ ′型沉淀物（Ni_3X，X = Al，Ga，Ge或Si）粗化的几个新方面进行了探索。 其中包括：（1）进一步研究小体积分数fv下的异常粗化动力学;（2）定量表征fv小时γ '沉淀物获得的凹立方形貌的演变，以及表征最终导致镍基γ/γ'合金中筏化的空间相关性;（3）利用磁分析研究了Ni-X合金（包括Ni-Ti合金）在低温（T550 ℃）下的γ ′粗化，定量测量了共格应变和fv对平衡共格溶解极限的影响。 提出了开展二元Al-Sc合金中Al_3Sc析出相粗化动力学研究的新课题。 分析的主要方法是暗场透射电子显微镜（TEM），图像分析软件应用于扫描的TEM底片，磁分析，以测量在镍基合金的γ '粗化过程中的基质的溶质浓度的变化，和电阻率，使在铝钪合金的可比测量。 这项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，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. ***