NSF Young Investigator

小行星9457964 已知金属间合金中的位错运动受位错核几何形状的支配，但利用这一知识的尝试已被目前可用的少量实验观察所抑制。 这项研究，这是独一无二的，它提供了一个非常定量的测量位错核心的几何形状相结合的透射电子显微镜与计算机生成的图像模拟，提供了一种方法，实验观察和表征金属间化合物合金中的位错核心结构。 这些定量的观察是用来链接的位错核心的原子结构与宏观力学性能在几种不同的金属间化合物合金。 已知向镍-锗中添加铁降低了异常流动强度行为，并最终导致合金中流动强度随温度升高而“正常”降低。 变形的一系列试样，系统地变化的铁含量和相关的测量故障能量与个别合金的屈服行为将提供有价值的信息的来源的流动强度异常的所有L12合金。 对金属间化合物合金中位错运动控制过程的基本理解将使合金设计者能够修改合金化学计量，以最大限度地提高延展性和高温强度。 ***

9457964 Hemker Dislocation motion in intermetallic alloys is known to be governed by the dislocation core geometry, but attempts to capitalize on this knowledge have been inhibited by the small number of experimental observations currently available. This study, which is unique in that it provides a very quantitative measure of dislocation core geometries by combining transmission electron microscopy with computer generated image simulations, provides a way of experimentally observing and characterizing dislocation core structures in intermetallic alloys. These quantitative observations are used to link the atomic structure of dislocation cores with the macroscopic mechanical properties in several different intermetallic alloys. It is known that the addition of iron to nickel-germanium reduces the anomalous flow strength behavior and eventually results in alloys in which the flow strength decreases "normally" with increasing temperature. Deforming a series of specimens that vary systematically in iron content and relating the measured fault energies with the yielding behavior of the individual alloys will provide valuable information about the sources of the flow strength anomaly in all L12 alloys. %%% A fundamental understanding of the processes that control dislocation motion in intermetallic alloys will allow alloy designers to modify alloy stoichiometry to maximize both ductility and high temperature strength. ***