Formation of quasicrystalline phases in Al-rich Al-Mn-Be alloys

Abstract

The effect of Be addition on the formation of quasicrystalline phases in Al-rich Al-Mn(-Be) alloys has been investigated. A metastable icosahedral quasicrystalline phase was found to form in a 93.5Al-5Mn-1.5Be (in wt%) alloy prepared by a conventional casting technique, indicating that the addition of Be to Al-Mn alloys improves the quasicrystal forming ability. The icosahedral phase in conventionally cast Al-Mn-Be alloys forms in the undercooled melt with the equilibrium growth morphology of the pentagonal dodecahedron. Heat treatment at 540 degreesC for 100 h results in the precipitation of small platelets of a two-dimensional quasiperiodic phase in the alpha-Al matrix. These precipitates have an orientation relationship with the a-Al. matrix. (C) 2004 Elsevier B.V. All rights reserved.