Author:J. Fikara, R. Schaller, N. Baluc

Institute: Federal Polytechnic School of Lausanne, IPMC, Lausanne 1015, Switzerland

Mechanical spectroscopy of quasicrystalline Al–Cu–Fe coatings is a unique method of analysis that allows studying the structural and mechanical characteristics of materials with quasicrystalline symmetry. Quasicrystals, possessing unique anomalous properties, differ from traditional crystals by a rare level of symmetry, which makes their study especially relevant in modern materials science.

In the study of mechanical properties of Al-Cu-Fe coatings obtained by various methods, such as sputtering or electrolytic deposition, an important aspect is the study of the relationship between microstructure and mechanical strength. The spectroscopy method allows not only to determine the elasticity and strength moduli, but also to identify characteristic resonance frequencies associated with internal defects.

The application of mechanical spectroscopy to quasi-crystalline coatings opens up new horizons in the search for materials with improved wear and thermal stability. This approach also contributes to a further understanding of the physical processes occurring in these unique structures, which may have practical implications in a variety of industries, including electronics and aerospace.

The internal friction of this composite was estimated using a forced-rotation pendulum, which allowed the internal friction level of the quasicrystalline coating itself to be calculated. The highest peak of internal friction was observed at about 600K. The quasicrystalline shell, thermally sprayed onto a steel substrate, was used for mechanical spectroscopic studies in the temperature range from 300 to 800K. Bulk Al–Cu–Fe quasi-crystals exhibited high brittleness at temperatures below 700K, which cast doubt on the results of isochronous measurements at 1 Hz, in contrast to isothermal ones. This peak can be associated with the relaxation of thermal stresses at the substrate–coating interface. These stresses also contribute to the anomalous increase in the shear modulus with increasing temperature. The exponential background at high temperatures is interpreted as a transition from a brittle to a ductile state in the quasicrystalline coating.

The introduction notes that polyquasicrystalline samples of Al–Cu–Fe alloy exhibit brittleness at room temperature and can be destroyed by cracks before reaching the yield point. Using mechanical spectroscopy aimed at studying plasticity, it was possible to identify the connections between phason defects and plastic properties of Al–Cu–Fe quasicrystals.

The experimental setup involved obtaining quasi-crystalline coatings from Sulzer Innotec AG with a thickness of about 500 µm, which was confirmed by analysis. The measurements were carried out on a vibrating rod and showed an increase in the internal friction of the composite with increasing coating thickness. The main results indicate that the main source of internal friction is the quasi-crystalline coating.

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