Atomic Scale Studies of Heterophase Metallic Interfaces

本研究的主要目的是检查在同一合金体系中形成的具有良好特征的共相干和半共相干异相界面上的偏析。试样制备主要通过固态分解反应或内部氮化来产生具有原子清洁界面的沉淀。接下来是低温处理，以诱导三元或四元元素的偏析。在一个临界直径以下，析出相是共相干的，而在这个直径以上，它们是半共相干的，允许在共相干或半共相干界面上研究偏析。采用了最高分辨率的技术，包括原子探针场离子显微镜和三维原子探针显微镜，高分辨率和扫描透射电子显微镜，以及空间分辨电子能量损失光谱。在被调查的系统中，包括技术感兴趣的界面和“模型”界面，有Al/Al3Sc (Mg)（航空航天结构合金）；Al（Cu）和Cu(Sn或In)（集成电路互连）；Fe / Mo, Fe / Mo (V);α - fe /钼氮化（Sn）；Au/Ni，有或没有分离。异相界面的理论建模解决了界面结构和界面上分离体的性质。模型采用从头算密度泛函理论计算、分子动力学和蒙特卡罗模拟以及连续介质弹性理论。原子偏析在技术上意义重大的异相金属界面的物理力学性能中起着至关重要的作用。分离体对于调整界面特性很重要，例如，通过引入选定的微合金化溶质来控制数量。从相干析出物到半相干析出物的临界转变直径的控制在技术上是很重要的，因为它决定了材料微观结构的稳定性。＊＊＊

9728986 Seidman The principal thrust of this study is examination of segregation at well-characterized coherent and semicoherent heterophase interfaces developed in the same alloy system. Specimen preparation is achieved primarily via solid-state decomposition reactions or internal nitridation to produce precipitates with atomically clean interfaces. This is followed by low-temperature treatments to induce segregation of ternary or quaternary elements. Below a critical diameter the precipitates are coherent, while above this diameter they are semicoherent, allowing a study of segregation at either coherent or semicoherent interfaces. The highest resolution techniques available, including atom- probe field-ion and three-dimensional atom-probe microscopies, high-resolution and scanning transmission electron microscopies, and spatially resolved electron- energy-loss spectroscopy, are employed. Among the systems investigated, which include both interfaces of technological interest and `model' interfaces, are Al/Al3Sc (Mg) (an aerospace structural alloy); Al(Cu) and Cu(Sn or In) (interconnects for integrated circuits); Fe/Mo, Fe/Mo(V); alpha-Fe/molybdenum nitride (Sn); Au/Ni, with and without segregants. Theoretical modeling of heterophase interfaces addresses the interface structure and the properties of the segregants at the interfaces. The modeling employs ab initio density functional theory calculations, molecular dynamics and Monte Carlo simulations, and continuum elasticity theory. %%% Segregating atoms play a crucial role in the physical and mechanical properties of technologically significant heterophase metallic interfaces. Segregants are important for tailoring interfacial properties, e.g., by the introduction of selected microalloying solutes in controlled quantities. Control of the critical transition diameter from coherent to semicoherent precipitates is technologically important, as it determines the stability of the microstructure of the m aterial. ***