On the evolution of quasicrystalline and crystalline phases in rapidly quenched Al-Co-Cu-Ni alloy

Abstract

The occurrence of stable decagonal quasicrystalline phase in Al-Co-Ni and Al-Cu-Co alloys through conventional solidification is well established. Earlier, we have studied the effect of Cu substitution in place of Co in the Al70Co15Ni15 alloy. Here we report the structural/micro-structural changes with substitution of Cu for Ni in rapidly solidified Al-Co-Ni alloys. The melt spun ribbons have been characterized using X-ray diffractometry, scanning and transmission electron microscopy. With an increase in Cu content in the melt spun Al70Co15CuxNi15-x (x = 0-15 at.%) alloys, the relative amount of the decagonal phase decreased up to 10 at.% of Cu. At this composition, the quaternary alloy showed the co-existence of decagonal quasicrystal and superstructure of τ3 vacancy ordered crystalline phases. The decagonal phase containing Cu showed more disordering than Al-Co-Ni alloys. The implication of the structural and microstructural changes due to Cu substitution in stable decagonal quasicrystals will be discussed. © 2006 Elsevier B.V. All rights reserved.