Atomic Scale Studies of Heterophase Metallic Interfaces

9728986塞德曼这项研究的主要目的是检查同一合金系统中形成的具有良好特征的、连贯的和半粘合的异相界面上的偏析。样品的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物。其次是低温处理，以诱导三元或四元元素的偏析。在临界直径以下，析出物是共格的，而在这个直径以上，它们是半粘合的，这使得可以研究在共格或半粘合界面上的偏析。使用了现有的最高分辨率技术，包括原子探针场离子和三维原子探针显微镜，高分辨率和扫描电子显微镜，以及空间分辨电子能量损失谱。在所研究的系统中，既包括技术感兴趣的界面，也包括“模型”界面，包括Al/Al3Sc(镁)(一种航空航天结构合金)；Al(铜)和铜(锡或铟)(集成电路的互连)；铁/钼、铁/钼(V)；α-铁/氮化钼(锡)；金/镍，带和不带分隔剂。异相界面的理论模型解决了界面结构和界面上的分离剂的性质。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。偏析原子在具有重要技术意义的异相金属界面的物理和机械性能中起着至关重要的作用。分割剂对于调整界面性能很重要，例如，通过引入受控数量的选定微合金化溶质。控制从共格析出物到半粘性析出物的临界转变直径在技术上很重要，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. ***