Atomic Structure, Growth Mechanisms and Kinetics of Precipitate Interfaces in Metal Alloys

小行星9630092 这项研究工作采用高分辨率分析电子显微镜来解决几个基本的问题，在金属合金中的沉淀界面的界面结构和生长动力学。 具体地，使用配备有能量色散X射线光谱仪（EDS）的场发射透射电子显微镜（TEM）的高分辨率（0.14 nm图像分辨率）、小探针（0.5 nm直径）能力来确定围绕在Al-Ag合金中的γ沉淀物板的表面上的生长壁架和板边缘的扩散场（溶质浓度分布）。 这些数据进行了比较，从理论模型中获得的浓度分布，以提供这些模型的第一次测试。 在同一显微镜上的Gatan成像滤波器（GIF）与0.5 nm探头一起使用，以获得电子能量损失谱（EELS）在Ti-H合金中的γ氢化物板的面，边缘和壁架。 这些数据使得有可能确定氢化钛结构是否完全形成在变换界面处，或者组成和结构变化是否可以在该混合模式变换中解耦。这种分析应该澄清与金属合金中沉淀物板的生长有关的关键基本问题。 这项实验研究为理论工作者提供了重要的信息，在生长的早期阶段，在生长的沉淀物板的表面上的壁架附近的浓度分布。Ti-H合金研究探索了Ti的剪切是否允许氢化钛TiH生长的问题。 目前，氢化物的生长机理尚不清楚，但氢化物是钛合金中不希望出现的相。 ***

9630092 Howe This research effort employs high-resolution analytical electron microscopy to address several fundamental questions concerning the interfacial structure and growth kinetics of precipitate interfaces in metal alloys. Specifically, the diffusion fields (solute concentration profiles) surrounding growth ledges on the faces of gamma precipitate plates and the plate edges in an Al-Ag alloy are determined using the high-resolution (0.14 nm image resolution), small-probe (0.5 nm diameter) capabilities of a field-emission transmission electron microscope (TEM) equipped with an energy-dispersive X-ray spectrometer (EDS). These data are compared with concentration profiles obtained from theoretical models to provide the first tests of these models. The Gatan imaging filter (GIF) on the same microscope is used in conjunction with the 0.5 nm probe to obtain electron energy-loss spectra (EELS) across the faces, edges and ledges of gamma hydride plates in Ti-H alloys. These data make it possible to determine whether the titanium hydride structure is fully formed at the transformation interface or whether the compositional and structural changes may be decoupled in this mixed-mode transformation. Such analyses should clarify key fundamental questions related to the growth of precipitate plates in metal alloys. %%% This experimental research provides theorists important information on the concentration profiles in the vicinity of ledges on the faces of growing precipitate plates during early stages of growth. Ti-H alloy research explores the question of whether shear of Ti permits the titanium hydride, TiH, to grow. The mechanism of growth is obscure at the present time, but the hydride is an undesirable phase in titanium alloys. ***