Contribution to Al-Pd-Co system: Structural studies of epsilon phase and proposal of partial isothermal section at 1035 °C

Abstract

The aim of this work was to propose the experimental partial isothermal section of the Al-Pd-Co phase diagram at 1035 °C and to study the structure of quasicrystalline approximant εn. Scanning electron microscopy including energy dispersive X-ray spectroscopy, X-ray diffraction and scanning transmission electron microscopy were used in the investigation. Calculation of atomic structures was performed using Monte Carlo simulation minimising Empirical Oscillating Pair Potentials energy. Besides the proposed partial isothermal section at 1035 °C, homogeneity ranges of phases εn, U, F, V, δ, and W were schematically projected. Various modifications of εn were observed and/or identified in the investigated alloys. The structures of ε22 and ε34 were experimentally observed in the Al-Pd-Co system for the first time. Furthermore, their atomic structure models were created. Last but not least, it was experimentally documented that the regular arrangement of tiles in εn structures can be interrupted by structural defects. The obtained results form a comprehensive picture of the individual structural modifications of the εn phase.