Density, Young’s modulus, specific heat, and stability of icosahedralAl86Mn14

Abstract

The melt-spun icosahedral phase of ${\mathrm{Al}}_{86}$ ${\mathrm{Mn}}_{14}$ exhibits a density (=3.26±0.06 g/${\mathrm{cm}}^3$) only slightly less dense by ∼1% and a specific heat higher by ∼0.20 cal/mol K compared with the stable orthorhombic phase. The room-temperature Young’s modulus, however, is found to decrease drastically by ∼20% from 12.60×${10}^{11}$ dyn/${\mathrm{cm}}^2$ for the orthorhombic phase to 10.12×${10}^{11}$ dyn/${\mathrm{cm}}^2$ for the icosahedral phase. The activation energy and heat of the icosahedral-orthorhombic transformation are found to be 53 kcal/mol and 560 cal/mol, respectively. The changes in these physical properties observed here are in many ways similar to those reported for many metal glasses. It is thus inferred that the icosahedral ${\mathrm{Al}}_{86}$ ${\mathrm{Mn}}_{14}$ consists of a highly disordered defective structure.