CHEMICAL ORDER IN AN AL-PD-MN ICOSAHEDRAL QUASI-CRYSTAL

The icosahedral structure of Al70Pd20Mn10and Al65Cu20Fe15quasicrystals in rapidly solidified and annealed states has been examined by electron and X-ray diffraction techniques. Broadening and distortion of the diffraction peaks due to atomic disordering were observed in rapidly solidified Al65Cu20Fe15, but were not observed in rapidly solidified Al70Pd20Mn10. The rapidly solidified Al70Pd20Mn10quasicrystal has a highly ordered atomic arrangement which is nearly the same as that for an Al65Cu20Fe15quasicrystal annealed at a temperature just below the melting point. On the basis of the thermodynamical data, it is presumed that a strong chemical order(bonding) between Pd and A1 or Mn prevents the Al70Pd20Mn10quasicrystal from generating atomic disordering and phason strains during rapid solidification. © 1990 Taylor & Francis Group, LLC.