Structurally complex alloy phases: Structure, defects and mechanical properties

本项目重点研究了几种结构复杂的巨型晶胞合金相（SCAP）的结构、缺陷和塑性变形特性。所选择的材料有：_ - al3mg2， C2-Al-Pd-Fe以及Al-Pd-Mn体系中的正交双相和正交双相。其他阶段将在项目期间引入。这些材料将以单相生长，如果可能的话，将以单晶形式生长。该结构将采用x射线衍射、电子衍射和高分辨率电子显微镜进行晶体学表征。生长的晶格缺陷将通过透射电子显微镜（TEM）在布拉格对比度和高分辨率下进行表征。单相和单晶样品将在单轴试验机的高温下发生塑性变形。为了定量地阐明变形过程的本质，将对塑性变形过程的宏观塑性变形行为进行表征，并确定塑性变形过程的热力学激活参数。利用高分辨率透射电镜对变形引起的缺陷结构，如位错、平面断层和剪切线进行研究。Bragg-contrast和会聚光束技术将被应用于位错排列、应变场和Burgers向量的测定。这将允许深入了解这些材料目前未知的塑性变形机制。

This project focuses on the experimental investigation of the structure, defects and plastic deformation properties of a number of selected structurally complex alloy phases (SCAP) with giant unit cells. Materials of choice are e.g. _ -Al3Mg2, C2-Al-Pd-Fe and the orthorhom-bic_ '- and _ -phases in the Al-Pd-Mn system. Other phases will be introduced during the project. These materials will be grown in single phase and, if possible, single crystalline form. The structure will be characterized crystallographically employing X-ray diffraction, electron diffraction and high-resolution electron microscopy. Grown-in lattice defects will be characterized by transmission electron microscopy (TEM) both in Bragg contrast and in high-resolution. Single-phase and single-crystalline samples will be deformed plastically at ele-vated temperatures in an uniaxial testing machine. In order to clarify the nature of the deformation process quantitatively, the macroscopic plastic deformation behavior will be characterized and the thermodynamic activation parameters of the plastic deformation process will be determined. The deformation-induced defect structure, e.g. dislocations, planar faults and shear lines, will be investigated by high-resolution TEM. Bragg-contrast and convergent-beam techniques will be applied for the determination of dislocation arrangements, strain fields and Burgers vectors. This will allow to gain insight into the currently unknown plastic deformation mechanisms of these materials.