Quasicrystals, possessing a unique atomic structure combining order and non-periodicity, attract considerable attention from researchers due to their unusual physical properties. Among them, a special place is occupied by aluminum-copper-iron (Al-Cu-Fe) alloys, known for their high stability and potential for application in various fields, including protective coatings and catalysis. In this paper, we focus on the study of the mechanical and surface properties of Al-Cu-Fe thin films obtained by magnetron sputtering.
Mechanical properties such as hardness and elastic modulus were investigated using nanoindentation. The results obtained demonstrate that the Al-Cu-Fe thin films have high hardness, comparable to that of some metallic glasses. This fact indicates their potential for use as wear-resistant coatings. In addition, the elastic modulus of the films, determined from the loading curves, also shows high values, indicating significant rigidity of the material.
Surface properties, including roughness and wettability, were investigated using atomic force microscopy and contact angle measurements. The analysis showed that the Al-Cu-Fe thin films have a relatively smooth surface, which is an important factor for applications in microelectronics and optics. The contact angle measured for various liquids indicates that the surface of the films has hydrophobic properties.
The formation of quasi-crystalline structure by annealing multilayer films consisting of Al, Cu and Fe is demonstrated. Thermal treatment parameters affect the mechanical characteristics and surface properties of the obtained quasicrystals. In this study, multilayer Al-Cu-Fe thin films of different elemental compositions were deposited on Si/SiO2 substrates and subjected to two-step annealing with different durations (5, 10 and 15 hours).
The results of X-ray diffraction analysis revealed that the sample annealed for 15 hours exhibits a more pronounced quasi-crystalline peak, indicating increased phase stability compared to other phases present. Based on the diffraction data, the percentage content of each phase was estimated. It was found that the sample with the longest annealing is characterized by the predominance of the ψ-phase (84.3% of the total volume of the crystalline quasi-crystalline phase) and an insignificant presence of the cubic phase Al50(CuFe)50.
Nanoindentation testing and contact angle measurements showed that this sample has the highest hardness (∼11 GPa) and the largest contact angle (127°).
The obtained results indicate the prospects of using thin Al-Cu-Fe films as functional materials with unique mechanical and surface properties. Further research will be aimed at optimizing the conditions for obtaining films and studying their behavior under various operating conditions.
Author: Hadi Parsamehr, Shou-Yi Chang, Chih-Huang Lai
Institute: Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, 30013, Taiwan