Icosahedral quasicrystals display irregular shape if it is embedded in bulk material. If it has free surface, it has well-defined facets, reflecting its unique 5-, 3-, and 2-fold rotational symmetries. In this study, an Al-Cu-Fe alloy with nominal composition of Al 65 Cu 20 Fe 15 was prepared by arc melting and the microstructure was studied by using Scanning Electron Microscope, Energy Dispersive X-ray Spectroscopy, and Electron Back Scattering Diffraction (EBSD). On the surface of λ crystalline phase, an extra layer is found. EBSD from this layer revealed 5-, 3-, and 2-fold rotational symmetries, demonstrating the icosahedral quasicrystalline structure. Further, it has been found that the icosahedral quasicrystalline extra layer and the λ substrate have orientation relationship revealed by the coincidences of Kikuchi bands and poles on the EBSD patterns. This report is important to future studies regarding the formation of icosahedral quasicrystalline phase and thin film preparation related to icosahedral quasicrystalline phase.

It is well known that when particle size is reduced, surface effect becomes important. As a result, micro/nanoparticles tend to have well defined geometric shapes to reduce total surface energy, as opposed to the irregular shapes observed in most bulk materials. The surface of such micro/nanostructures are smooth. Any deviation from a smooth surface implies an increased surface energy which is not energetically favorable. Here, we report an observation of spherical particles in an alloy of Al65Cu20Fe15 nominal composition prepared by arc melting. Such spherical particles stand out from those reported so far due to the decoration of concentric nanorings on the surface. Three models for the formation of these concentric ring patterns are suggested. The most prominent ones assume that the rings are frozen features of liquid motion which could open the door to investigate the kinetics of liquid motion on the micro/nanometer scale.

No abstract

No abstract