The substructure of quasicrystalline Al-Mn alloy observed by TEM

The morphology of the icosahedral phase in Al₈₆Mn₁₄ alloy has been observed as flower-like and of granular shape by TEM. These two kinds of morphologies may be regarded as the different sections of a three-dimensional flower-like grain. Inside these grains, a fine substructure of a few nm in size has been found. A dendritic morphology with a diffraction pattern showing five-fold symmetry have also been observed in the Al₈₆Mn₁₄ alloy. On the basis of these observations, a model based on nucleation, growth and aggregation has been proposed to explain the formation process of the quasicrystalline state.