Shock synthesis of Al-Fe-Cr-Cu-Ni icosahedral quasicrystal

Abstract

Al-alloy quasicrystals (QC) are of great interest because of their unique physical properties and natural occurrence in a meteorite. Considerable effort has been invested to explore the compositional fields of stable QC and quenchable metastable QC. In this light, shock recovery experiments, originally aimed at proving the planetary impact origin of natural quasicrystalline phases, also offer a novel strategy for synthesizing novel QC compositions and exploring expanded regions of the QC stability field. In this study, we shocked an Al-Cu-W graded density target (originally manufactured for use as a ramp-generating impactor but here used as target) to sample interactions between 304 stainless steel and the full range of Al/Cu starting ratios. This experiment synthesized an icosahedral quasicrystal of new composition Al₆₈Fe₂₀Cr₆Cu₄Ni₂. No previous reports of Al-Fe-Cr QCs have reached such high Fe/Cr ratio or low Al content. The Cr+Ni content is at the upper bound of this low-Cu quinary icosahedral QC according the Hume-Rothery rules for stability. Our synthesis suggests that the presence of Cu promotes the incorporation of Cr+Ni in the Al-rich icosahedral QC phase, enabling the high Fe/Cr ratio observed.

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