Structurally complex alloy phases: Structure, defects and mechanical properties

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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.