Formation of icosahedral quasicrystals in an annealed Zr65Al7.5Ni10Cu12.5Ag5 metallic glass

The formation and thermal stability of an icosahedral quasicrystalline phas e in an annealed Zr65Al7.5Ni10Cu12.5Ag5 metallic glass have been investigat ed by Xray diffraction and transmission electron microscopy analyses. It wa s found that the quasicrystalline phase can precipitate from the glassy sta te and the supercooled liquid of the alloy over a wide range of annealing t emperatures. After optimizing the heat-treatment conditions, the volume fra ction of the quasicrystalline phase in the alloy can reach as high as about 80%. Investigation of the thermal stability of the quasicrystalline phase demonstrates that it is very stable when the annealing temperature is below the glass transformation temperature T-g of the alloy.