On the Evolution of Quasicrystalline and Crystalline Phases in Rapidly Quenched Al-Co-Cu-Ni Alloy

TL;DR

This study investigates how substituting Cu for Ni in rapidly quenched Al-Co-Ni alloys affects their structural phases, revealing a decrease in decagonal quasicrystal content and increased disorder with higher Cu levels.

Contribution

It provides new insights into the microstructural evolution and phase stability in Al-Co-Cu-Ni alloys during rapid solidification, especially regarding Cu's impact on decagonal quasicrystals.

Findings

Decagonal phase decreases with Cu substitution up to 10 at%.

Coexistence of decagonal quasicrystal and tau 3 crystalline phases at specific compositions.

Cu substitution leads to increased disorder in the decagonal phase.

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 Al70 Co15Ni15 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 (XRD), Scanning and transmission electron microscopy (SEM & TEM). With an increase in Cu content in the melt spun Al70 Co15Cux Ni15-x (x=0 to 15) alloys, the relative amount of the decagonal phase decreased up to 10 at% of Cu. At this composition the quaternary alloy showed the coexistence of decagonal quasicrystal and superstructure of tau 3 vacancy ordered crystalline phases. The decagonal phase containing Cu showed more disordering compared to Al-Co-Ni alloys. The implication of the structural / microstructural changes due to Cu substitution in stable decagonal quasicrystal will be discussed