Precipitation of multi-type nano-quasicrystals in a Mg-Zn-Y alloy

Mg-6Zn-1Y (at.%) ribbons with strengthening precipitates of multi-type nanoquasicrystals were prepared by melt-spinning followed by aging treatments. Microstructural evolution of the rapidly solidified ribbons during isothermal aging was comprehensively studied using various electron microscopy techniques. Two new kinds of decagonal quasicrystals were formed in aged ribbons, in addition to precipitation of nanometer icosahedral quasicrystals. Atomic-resolution observations reveal that both decagonal quasicrystals can be modeled by quasi-periodic tiling with decagonal clusters of 2.5 nm in diameter, but overlap of neighboring clusters in both decagonal quasicrystals is different from the Gummelt model observed in other quasicrystals. A shell composed of complex Laves Mg-Zn domains was formed surrounding each decagonal quasicrystal precipitate upon prolonged aging. In addition, all kinds of nanoprecipitates exhibit excellent structure and size stability at 573 K. Our findings may have implications for not only fundamental studies about quasicrystals, but also microstructural manipulation of high-performance Mg alloys.