Quasicrystal formation in gas-atomized Zr₈₀Pt₂₀ powders

Abstract

Gas-atomized powders with a nominal composition of Zr₈₀Pt₂₀ have been investigated as a function of powder size range. Atomized powders were screened to the following sizes for examination: <10 µm; +10, −20 µm; +20, −45 µm; +45, −75 µm; +75, −106 µm. For comparison of as-synthesized structure and crystallization behaviour, Zr₈₀Pt₂₀ melt-spun ribbons (MSRs) were also prepared. Results show that during atomization a metastable quasicrystalline (QC) phase is formed as the predominant phase independent of powder size; a small volume of amorphous phase and crystals were detected in finer and coarser sized powders, respectively. The QC grains formed during atomization are much larger than the nanosized quasicrystal obtained in the MSR, which is most likely attributed to the much slower cooling rates during gas atomization. Nucleation and growth occur during both rapid solidification routes. The formation of an icosahedral quasicrystal during gas atomization and melt spinning is consistent with previous suggestions that icosahedral local structure exists in liquid and amorphous phases and facilitates nucleation of quasicrystal formation in Zr₈₀Pt₂₀ alloys.

Acknowledgements

This work is supported by the US Department of Energy through Iowa State University under contract no. W-7405-ENG-82.