Icosahedral-Phase Formation by Solid-State Interdiffusion

Abstract

We have formed the icosahedral phase in ${\mathrm{Al}}_{86}$ ${\mathrm{Mn}}_{14}$, ${\mathrm{Al}}_{82}$ ${\mathrm{Mn}}_{18}$, and ${\mathrm{Al}}_{75.5}$ ${\mathrm{Mn}}_{20}$ ${\mathrm{Si}}_{4.5}$ alloys by the interdiffusion of elemental layers in the solid state. Annealing at 250-425°C produced the phase in times as short as 1 min with grains up to ∼ 14 nm in diameter. Continued annealing transformed the alloy layers into crystalline phases. These results demonstrate that the icosahedral phase nucleates in the solid state in preference to crystalline phases of lower free energy, even though the initial material does not have liquidlike icosahedral short-range order.