Microstructure, fabrication and properties of quasicrystalline Al-Cu-Fe alloys: a review

Quasicrystalline materials constitute a new materials group with certain crystalline structural characteristics, such as the generation of Bragg peaks in the X-ray data and points in the electron diffraction pattern, but translational symmetry is forbidden for crystalline materials. Thus, there exists aperiodicity in the structure of quasicrystalline materials. Besides being theoretically interesting due to their complicated atomic structure, the unique properties of quasicrystalline materials-low electrical and thermal conductivity, unusual optical properties, low surface energy and coefficient of friction, oxidation resistance, biocompatibility and high hardness, to name a few-also make them interesting for many practical purposes. Quasicrystalline phases are today encountered in over 100 alloy systems, of which the majority are aluminium based. Few of the alloying elements used to form aluminium-based quasicrystals are reasonable in price, easily available and non-toxic. However, quasicrystalline Al-Cu-Fe ternary alloys fulfill all these alloying-element criteria. In this paper, the microstructure, fabrication and properties of quasicrystalline Al-Cu-Fe alloys are reviewed from the perspective of materials engineer. The paper discusses the microstructure and metallurgy of quasicrystalline Al-Cu-Fe alloys. The preparation methods of quasicrystals in general and their application to the fabrication of Al-Cu-Fe quasicrystalline alloys are considered. The characteristics of different production methods, including both conventional methods yielding stable phases and more advanced methods introducing metastable phases, are compared in this paper. The properties of Al-Cu-Fe quasicrystals are also reviewed, aiming at a better understanding of the basic differences between crystalline and quasicrystalline materials with respect to structure and properties. Finally current and possible future applications of Al-Cu-Fe quasicrystals are discussed in the light of their properties. (C) 2003 Elsevier B.V. All rights reserved.