Structural relaxation in theAl86Mn14quasicrystal

Abstract

Calorimetric and Young’s-modulus measurements reveal that the as-spun ${\mathrm{Al}}_{86}$ ${\mathrm{Mn}}_{14}$ quasicrystal exhibits structural relaxation at temperatures well below the icosahedral-orthorhombic transition. The enthalpy of relaxation is ≃90 cal/mol and the Young’s modulus increases by ∼1%. The annealed samples upon heating show a reversible endothermic reaction of an elastic origin which is also reflected in the appearance of loss modulus. The activation energies of relaxation range from 42 to 51 kcal/mol. The relaxation behaviors of the ${\mathrm{Al}}_{86}$ ${\mathrm{Mn}}_{14}$ quasicrystal are in many ways very similar to those of glassy ${\mathrm{Al}}_{50}$ ${\mathrm{Si}}_{30}$ ${\mathrm{Mn}}_{20}$ and ${\mathrm{Pd}}_{77}$ ${\mathrm{Cu}}_6$ ${\mathrm{Si}}_{17}$.