New Stable Icosahedral Al-Cu-Ru and Al-Cu-Os Alloys

Abstract

A thermodynamically stable quasi-crystalline single phase with an icosahedral structure was found to be formed at atomic compositions of Al 65 Cu 20 Ru 15 and Al 65 Cu 20 Os 15 in conventionally solidified and fully annealed states as well as in a rapidly solidified state. The quasi-crystalline nature determined by X-ray diffractometry is the highest for the fully annealed ingot, indicating the existence of a truly equilibrium icosahedral structure. The stable quasi-crystals appear to have a growth morphology of pentagonal dodecahedron with an average size of 0.03 mm in a fully annealed state.