Rapidly Solidified Metallic Alloys with Unusual Symmetry Properties

摘要

We have synthesized a new class of metallic glasses based on aluminum. Theunusual structural and formality of these glasses have been investigated by x-ray and neutron diffraction, and by high-resolution electron lattice imaging experiments. The glassy nature is confirmed and a dense-random-packing of rare-earth atoms is observed. This new class of aluminum-based metallic glasses has a low density, high tensile strength, and good corrosion-resistant properties which are important for technological applications. We have also performed extensive structural studies of icosahedral and decagonal crystals. Diffraction measurements have been compared with atomic models proposed for quasicrystals. It is found that the decoration of Penrose tiling provides an adequate description of experimental findings in icosahedral crystals. In the case of decagonal crystals, there is strong evidence for an entropy stabilization mechanism. Structural defects in complex crystals closely related to icosahedral crystals have been studied. The defects have been found to be of the planar type and their structure forms the basis of icosahedral phase formation.