LONG-RANGE CHEMICAL ORDERING IN AL-CU-FE, AL-CU-MN, AND AL-CU-CR QUASI-CRYSTALS

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. © 1990, Materials Research Society. All rights reserved.