Solidification of Mg-28%Zn-2%Y alloy involving icosahedral quasicrystal phase

摘要

Applying XRD, DTA, SEM and TEM techniques, an investigation on the solidification microstructure and solidification sequence of Mg-rich Mg-28%Zn-2%Y (mole fraction) alloy was carried out. It is found that, α-Mg dendrites, Mg_7Zn_3 phase and icosahedral quasicrystal phase coexist in the as-solidified alloy, where the icosahedral quasicrystal, whose structure is indentified to be a face-centered type, originates from a peritectic reaction occurring at 416℃. The primary phase of this peritectic reaction has the composition of Mg_(20)Zn_(66)Y_(14), which is coincident with the H phase reported by TSAI as (Zn, Mg)_5Y. Furthermore, the single Ⅰ-phase grain morphology was observed and its growth evolution was also discussed.