Formation and stability of icosahedral phase in Al₆₅Ga₅Pd₁₇Mn₁₃ alloy

Abstract

The formation and characterization are described of a quaternary (pseudo-ternary) icosahedral quasicrystal in Al₆₅Ga₅Pd₁₇Mn₁₃ alloy. X-ray diffraction and transmission electron microscopy observations confirmed the formation of icosahedral, B2 type and ξ′ crystalline (orthorhombic structure with unit cell a = 23.5 Å, b = 16.6 Å and c = 12.4 Å) phases in as-cast alloy. The icosahedral phase is formed after annealing at 800°C for 60 h. This is the first report of the formation of an icosahedral phase in an Al–Ga–Pd–Mn quaternary alloy by present technique. The energy dispersive X-ray analysis investigations suggest the presence of Ga (∼5 at.%) in the alloy. Icosahedral Al–Ga–Pd–Mn provides a new opportunity to investigate various characteristics, including surface characteristics. Attempts are made to discuss the micromechanisms for the formation of the quasicrystalline phase in Al–Ga–Pd–Mn alloys.

Keywords:

• quasicrystal
• Al–Ga–Pd–Mn alloy
• phase transformation
• icosahedral phase

Acknowledgements

The authors would like to thank Prof. S. Ranganathan, Prof. P. Ramachandra Rao, Prof. G.V.S. Sastry, Prof. N.K. Mukhopadhyay, Prof. J.M. Dudois and Prof. K. Mandal for many stimulating discussions. The financial support from the Indo–French Centre for the Promotion of Advanced Research, CEFIPRA, DST, New Delhi is gratefully acknowledged. One of the authors (T.P. Yadav) acknowledges to Council of Scientific and Industrial Research (CSIR), New Delhi, for a Senior Research Fellowship, during which period the work was completed.