Two Al-Mn-Zn alloys in melt-spun condition have been studied by transmission electron microscopy. The Al_2Mn_5Zn alloy was found to be fully icosahedral, while the Al_12Mn_2.9Zn alloy gave rise to decagonal quasicrystal. The decagonal phase grew in clusters with an orientation relationship between the grains suggesting nucleation on an icosahedral seed. On annealing at 500-600 deg C, the quasicrystalline phases transformed to a body centered orthorhombic phase L (a = 1.24,b = 1.26 and c = 3.05 nm) with a hgh density of planar defects.
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