Icosahedral AlCuFe quasicrystals, having a unique atomic structure with a long-range order, do not have translational symmetry, which determines their unusual mechanical properties. One of the key parameters characterizing the mechanical behavior of these materials is the yield strength. Unlike conventional crystalline materials, where yield is associated with the movement of dislocations, in quasicrystals, deformation is carried out by other mechanisms, such as phonons, flips, and rearrangement of the atomic structure.
Determining the yield strength of icosahedral AlCuFe quasicrystals is a difficult task due to their brittleness at room temperature. Traditional tensile and compression testing methods often result in sample failure before plastic deformation is achieved. To overcome this problem, methods are used that allow testing at elevated temperatures or under hydrostatic pressure.
In order to establish the true factors causing this behavior, short-term creep tests were performed at the moment of reaching the yield point of icosahedral polyquasicrystalline AlCuFe materials. The obtained experimental data clearly show that the achievement of the yield point is predominantly due to the blocking of dislocation motion, and also demonstrate the presence of an interaction between the velocity of dislocation movement and the short-term recovery process.
The results of the study show that the yield strength of icosahedral AlCuFe quasicrystals depends significantly on temperature. At low temperatures, the material exhibits brittle behavior, while with increasing temperature, plastic deformation is observed. The deformation mechanisms also change with temperature. At low temperatures, deformation is likely associated with the formation and propagation of cracks, and at high temperatures – with plastic flow caused by the movement of atomic rearrangements. In addition, alloying and changing the composition of the AlCuFe alloy also affect the yield strength, allowing modification of the mechanical properties of these unique materials.
Author: M Texier, J Bonneville, A Proult, J Rabier, N Baluc, P Guyot
Institute: University of Poitiers, LMP, UMR-CNRS 6630, SP2MI, PO Box 30179, F-86962 Chassenelle, Futuroscope Cedex, France, Materials for Thermonuclear Fusion – Euratom Association – Swiss Confederation, CRPP – Federal Polytechnic School of Lausanne, CH-5232 Villigen, PSI, Switzerland, National Polytechnic Institute of Grenoble, UMR CNRS 5614, LTPCM, F-38042 Saint-Martin-d’Eures, France