Structural change from amorphous to nano icosahedral quasicrystalline phase with quenching rate in Zr-Pt binary alloy

J. Saida et al., Structural change from amorphous to nano icosahedral quasicrystalline phase with quenching rate in Zr-Pt binary alloy, MATER TRANS, 42(6), 2001, pp. 1103-1108
Citations number
Categorie Soggetti
Material Science & Engineering
Journal title
ISSN journal
1345-9678 → ACNP
Year of publication
1103 - 1108
SICI code
Structural change with quenching rate in the Zr80Pt20 alloy was studied by controlling the roll speed in the melt-spinning technique. The as-quenched ribbon had an amorphous structure at a roll speed of 50 ms(-1). An icosahed ral quasicrystalline phase was directly formed at a roll speed in the range of 40 to 30 ms(-1). The critical roll speed for the formation of the icosa hedral phase was 25 ms(-1), where the volume fraction of the icosahedral ph ase was very small. Several crystalline phases precipitated in the melt-spu n ribbon at roll speeds below 20ms(-1). The DSC curve of the sample prepare d at 50 ms(-1) clearly exhibited two exothermic peaks. The first exothermic peak at 717 K, corresponded to the transformation from the amorphous to th e icosahedral phase and the second peak was due to the decomposition reacti on of the icosahedral phase. The size of the icosahedral phase in the as-qu enched and annealed samples lay in the diameter range of 5 to 20 nm and the particles were distributed homogeneously. Thus, it was clarified that the nano icosahedral phase can be formed in the as-quenched state from the melt and in the annealed state from the amorphous phase in the Zr80Pt20 binary alloy. The icosahedral phase transformed to Zr, ZrPt, Zr9Pt11 and Zr5Pt3 ph ases at a temperature of approximately 900 K. The formation of the nano sca le icosahedral phase indicated the possibility that icosahedral short-range order exists in the melted state of the Zr-Pt binary alloy. The strong che mical affinity between Zr and Pt probably contributed to the stabilization of the icosahedral short-range order and restraining the long-range rearran gement of constitutional elements to form a stable crystalline phase, which is an important factor in the formation of an icosahedral phase.