Quasicrystals in Al-Pd-TM (TM=Transition Metal) Systems Prepared by Rapid Solidification

An icosahedral phase with a face-centered six-dimensional hypercubic lattice (F-type) and a decagonal phase were found to be formed in rapidly solidified Al-Pd-TM (TM=V, Cr, Mn, Fe, Co, Mo, Ru, Re or Os) and Al-Pd-Co alloys, respectively. The formation of the mostly single quasicrystalline phases is limited to the narrow compositional ranges with e/a between 1.6 and 1.8. Neither the simple cubic (P-type) icosahedral nor amorphous phase was found in the Al-Pd-TM system. Thus, the effect of the group number of TM on the rapidly solidified structure in the Al-Pd-TM alloys is significantly different from that for Al-Cu-TM alloys. On the basis of the thermodynamic data, it is presumed that the strong chemical bonding nature among the constituent elements in the Al-Pd-TM alloys prevents the formation of P-type icosahedral and amorphous phases.