The study of mechanical properties of AlCuFe alloys is of considerable interest from both fundamental and applied points of view. The presence of quasi-crystalline phases with a unique atomic structure in these alloys significantly affects their mechanical behavior. This paper examines the main aspects determining the mechanical properties of quasicrystals and crystalline phases in AlCuFe alloys.
Quasicrystals are characterized by long-range order but lack translational symmetry, which leads to a number of peculiarities in their mechanical behavior. In particular, quasicrystals exhibit high hardness and brittleness at room temperature. Deformation of quasicrystals occurs through the formation and movement of defects that differ from dislocations observed in ordinary crystals.
In AlCuFe alloys, crystalline phases such as Al2Cu and FeAl may be present along with quasi-crystalline phases. The mechanical properties of these phases are well studied and differ from those of quasi-crystals. Crystalline phases usually have higher plasticity and lower hardness compared to quasi-crystals.
The mechanical characteristics of icosahedral AlCuFe quasicrystals and their comparison with crystalline intermetallics of similar composition were studied using indentation and three-point bending. Quasicrystal structures are characterized by significant hardness (about 1000 HV) and increased elasticity (H/E> 0.08), but show low fracture toughness (). The presence of icosahedral inclusions in Al2Cu or AlFe matrices increases the resistance to crack growth to a critical state. In contrast to the brittle fracture of crystalline Al13Fe4, icosahedral quasicrystals exhibit an uneven, rough fracture surface. Signs of plastic deformation in quasicrystals are revealed, and considerations are proposed regarding the mechanism of this deformation.
The mechanical properties of AlCuFe alloys depend on the ratio of quasi-crystalline and crystalline phases. An increase in the content of the quasi-crystalline phase leads to an increase in hardness and brittleness, while an increase in the content of crystalline phases contributes to an increase in plasticity.
The mechanical properties of AlCuFe alloys are determined by complex interactions between quasicrystalline and crystalline phases. Understanding these interactions is necessary for the development of new materials with improved mechanical properties.
Author: U Köster, W Liu, H Liebertz, M Michel
Institute: Department of Chemical Engineering, University of Dortmund, W-4600 Dortmund 50, Germany