A QUASI-CRYSTAL WITH INFLATION SYMMETRY AND NO FORBIDDEN SYMMETRY AXES IN A RAPIDLY SOLIDIFIED MG-AL ALLOY

A new quasicrystal with no forbidden symmetry axes has been identified in a rapidly solidified Mg-61 at.% Al alloy. Its structure is charact erized by a cubic point group and aperiodic electron diffraction patte rns showing inflation symmetry. Therefore this new structural state of matter stands as a cubic quasicrystal. The ratios between inflated mo tifs are frequently close to irrational values related to root 3 (i.e. 1 + root 3, root 3 and (1 + root 3)/2). This quasicrystal is metastab le and transforms on annealing into the equilibrium fee beta phase (a = 2.83 nm).