Author: Ana Smontara, Jean-Claude Lasjaunias, Carley Paulsen, Ante Bilušić, Yvonne Calvayrac

Institute: Moscow State Institute of Steel and Alloys (Technological University), 119049, Moscow, Leninsky Prospekt, 4, Russia

The enthalpy of formation of the quasicrystalline phase and solid solutions in the Al-Fe-Cu system is a key aspect determining the thermodynamic properties of materials used in modern technologies. Given the complexity of interactions between the components of this system, several critical factors influencing the enthalpy can be identified.

The most significant are the degree of overlap of the electron shells, as well as the nature of the chemical bonds formed as a result of the interaction of atoms. Experiments show that the quasicrystals formed in this system have unique structural features, which in turn affects their stability and physical properties.

The standard enthalpies of formation of the quasicrystalline phase and ternary solid solutions in the Al-Fe-Cu system, as well as the intermetallic compound FeAl, were determined using solution calorimetry. The quasicrystalline phase was obtained by two different methods. The first method (I) involved ball milling of a mixture of pure aluminum, copper, and iron powders in a planetary mill, followed by hot pressing and annealing. The second method (II) implied arc melting of the components in an argon atmosphere, followed by annealing. This method was also used to obtain the FeAl compound and solid solutions. The phases were determined using X-ray diffraction analysis. The enthalpy of formation was determined for the quasicrystalline phase with the composition Al62Cu25.5Fe12.5 and for the ternary solid solutions bcc Al35Cu14Fe51, Al40Cu17Fe43, and Al50.4Cu19.6Fe30. The measured enthalpy of formation of the intermetallic compound FeAl is in good agreement with previously published results. The enthalpies of formation of quasicrystalline phases obtained by different methods have close values: −22.7±3.4 kJ/mol (method I) and −21.3±2.1 kJ/mol (method II).

Calculations of the enthalpy of formation of both the quasicrystalline phase and solid solutions are based on thermodynamic modeling methods, including approaches such as CALPHAD (Calculation of Phase Diagrams). These methods allow more accurate prediction of the behavior of materials under various temperature and pressure conditions, which is critical for their industrial applications. A detailed study of quasicrystalline structures and their properties opens up new horizons for applications in materials science and engineering.