Al-Cu-Fe quasicrystals are a unique class of materials that combine order but not periodicity in their atomic structure. Their stability and microstructure play a key role in determining their physical and mechanical properties, leading to potential applications in a variety of fields, including thermoelectricity, catalysis, and anticorrosive coatings.
The stability of the Al-Cu-Fe phase is a critical factor for maintaining the quasi-crystalline structure at various temperatures and operating conditions. Studies have shown that stability depends on the chemical composition and thermal history of the material. Deviations from the optimal stoichiometric ratio can lead to the formation of crystalline phases and the loss of the quasi-crystalline structure.
AlCuFe, called a new type of icosahedral quasicrystal, is distinguished by its ability to exist in both thermodynamically stable and unstable states. Additionally, it has been established that it has a face-centered structure. Intensive studies of this system in recent years have revealed a number of contradictory data. In particular, there is evidence of both a reversible and irreversible transition of the quasicrystalline phase to crystalline ones.
Also, based on Mössbauer spectroscopy, assumptions were made about the presence of discrete positions for transition metal atoms, which, however, were not confirmed by subsequent studies. The presence of vacancies in significant concentrations was detected. The combination of these factors calls into question the adequacy of existing structural models designed to explain the icosahedral organization observed in this system. In the proposed work, a critical review of various aspects characterizing the AlCuFe quasicrystal is presented.
The microstructure of Al-Cu-Fe quasicrystals, characterized by the presence of icosahedral grains, defects and grain boundaries, has a significant effect on their properties. Grains of the quasicrystalline phase usually have sizes from several nanometers to several micrometers. Grain boundaries can be a source of electron and phonon scattering, which affects their electrical and thermal conductivity.
The microstructure of Al-Cu-Fe alloys is studied using various methods, including electron microscopy (SEM, TEM) and X-ray diffraction. These methods allow visualization of the material structure at various scales and determination of the phase composition. Microstructure modeling based on molecular dynamics methods allows understanding the mechanisms of formation of the quasi-crystalline phase and its evolution over time.
Author: R.Divakar, D. Sundararaman, VS Raghunathan
Institute: Department of Physical Metallurgy, Metallurgical Division, Indira Gandhi Atomic Research Centre, Kalpakkam, TN 603 102, India