Long-range chemical ordering in Al-Cu-Fe, Al-Cu-Mn, and Al-Cu-Cr quasicrystals

The dependence of the F-type order and the stability of Al–Cu–Fe quasicrystals on quenching rate and composition are reported. In the Al–Cu–Mn and Al–Cu–Cr systems, where only metastable quasicrystals can be formed, a disordered icosahedral phase is obtained by melt-spinning, and P ⇉ F-type ordering is observed after annealing. Simultaneous evolution of the diffuse scattering and the ordering is observed as well. The quasicrystalline phases, P-type icosahedral as well as decagonal, in the ternary Al–Cu–TM alloys are structurally similar to those in the binary Al–TM alloys. Dislocations in the icosahedral phase have been imaged both by their strain field contrast and in high resolution.