The effect of Ag addition on the crystallization behavior of amorphous Zr₆₅Al_7.5Cu_17.5Ni₁₀Ag_x (x=0,2.5,5,7.5,10) Alloys

The effect of Ag on the crystallization behavior of rapidly solidified amorphous Zr₆₅Al_7.5Cu_17.5-xNi₁₀ Ag_x (X=0,2.5,5,7.5,10) alloys has been studied by using differential scanning calorimetry, X-ray diffractometry, and transmission electron microscopy. The amorphous phase in Zr₆₅Al_7.5Cu_17.5Ni₁₀ alloy crystallizes via coprecipitation of icosahedral phase and NiZr₂ phase in the first crystallization step, followed by decomposition of the quasicrystal into CuZr₂ and NiZr₂ phase. The NiZr₂ phase transformed to stable Zr₆NiAl₂ phase at high temperature. The alloys containing Ag crystallizes via a two step process: Firstly, quasicrystalline phase nucleates and grows in an amorphous matrix; Secondly, the quasicrystal and remaining amorphous transformed into a stable CuZr₂ and Zr₆NiAl₂ phases. With increasing Ag, the icosahedral phase becomes more thermally stable and the quasicrystals grain size decreased.