Mechanical properties and deformation behaviour of large Al₇₀Pd₂₀Mn₁₀ single quasi-crystals

An icosahedral single quasi-crystal of Al₇₀Pd₂₀Mn₁₀ was found to be deformed in the temperature range above 1000 K, accompanying the generation of a number of deformation markings. The deformation appears to occur inhomogeneously along the deformation bands which lie on the fivefold plane and the region in the deformation bands is identified to have deviated alloy compositions and approximant crystalline structures. As the test temperature increases, the density of the deformation markings increases accompanying the decrease in their spacing. Superplasticity is also obtained at temperatures above 0.98T_m, presumably because of the sliding at the interface between icosahedral and approximant crystalline phases. Furthermore, a number of dislocations are observed in the icosahedral phase deformed at temperatures above 1000 K and the dislocation density is much higher near the interface. The Burgers vector was analysed to have the twofold direction for the dislocations on the fivefold plane. It is therefore concluded that the icosahedral single quasi-crystal can be deformed via dislocations along the interface between icosahedral and approximant crystalline phases at temperatures above 1000 K.