Mechanochemical synthesis of icosahedral phases in Mg-Zn-Al and Mg-Cu-Al alloys

Mechanical alloying (MA) has been used to obtain the icosahedral phases: i-(Mg-Zn-Al) and i-(Mg-Cu-Al) from metal powders. X-ray diffraction peaks are identical to those of icosahedral obtained by the melt spun technique. SAD patterns from MA samples indicate 2,3,6 and 5-fold symmetry. Annealing of the MA icosahedral phases leads to the formation of related cubic Frank-Kasper phases, that can be transformed into the icosahedral phases by MA. The disclination network which appears in the cubic phase plastically deformed by MA seems to be intrinsic to producing an aperiodic phase with long-range icosahedral order.