Quasicrystalline Al-Cu-Fe alloys, which have unique physical and chemical properties, attract considerable attention from researchers and developers. Their microstructure and phase composition, which determine the functional characteristics, depend to a large extent on the processing and solidification conditions. Understanding these dependencies is critical for the targeted creation of materials with specified properties.
An important factor influencing the choice of phase is the cooling rate during solidification. Rapid cooling, achieved, for example, by melt quenching methods, promotes the formation of metastable quasicrystalline phases, while slow cooling leads to the formation of more stable crystalline phases. The alloy composition also plays a decisive role. Deviations from the stoichiometric ratio of Al, Cu and Fe can lead to the formation of different phase mixtures.
Heat treatment after solidification can modify the microstructure of the alloy. Annealing at certain temperatures promotes the growth of quasi-crystalline grains and can also lead to phase transformations aimed at achieving thermodynamic equilibrium. Mechanical treatment, such as rolling or drawing, can change the texture of the material and create the orientation of quasi-crystalline grains.
Quasicrystalline alloys of the Al-Cu-Fe system, differing in composition, were subjected to solidification under a number of experimental conditions. In particular, crucibleless electromagnetic levitation with varying degrees of supercooling, slow cooling in a DTA, moderate cooling rate in a water-cooled copper crucible, and quenching at a rate of 10^6 K/s were used.
The microstructural features and phase composition of the obtained samples were studied in detail using SEM, TEM and XRD methods. The obtained data are compared and analyzed from the standpoint of classical nucleation theory. The variety of solidification conditions made it possible to obtain samples with different microstructure and phase composition, which, in turn, made it possible to trace the effect of the cooling rate on the crystallization process.
Thus, the selection of the phase and microstructure of quasicrystalline Al-Cu-Fe alloys is a complex process that depends on many factors. Careful control of the processing and solidification conditions allows for the targeted formation of materials with the desired properties for specific applications. Further research is aimed at developing new processing methods and modifying the alloy composition to expand the range of possible properties and applications.
Author: D.Holland-Moritz, J. Schroers, B. Grushko, D.M. Herlach, K. Urban
Institute:
Institute of Solid State Physics, Forschungszentrum Juelich, D-52425 Juelich, Germany
Institute for Spatial Modelling, DLR, D-51170 Cologne, Germany
Institute for Experimental Physics IV, Ruhr-University Bochum, D-44780 Bochum, Germany