Precipitation of Icosahedral Phase in Zr-Ni-Nb-Cu-Al Metallic Glasses

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The crystallization behaviors of Zr-Ni-Nb-Cu-Al metallic glasses are greatly influenced by the substitution of Ni for Zr. For the glassy Zr_71−xNi_xNb₃Cu₁₆Al₁₀ (x=7, 9, 11 at%) alloys, the onset temperature of crystallization T_x increases from 717 to 748 K with increasing Ni content from 7 at% to 11 at%. The primary crystallization reaction of the studied glassy alloys corresponds to the formation of icosahedral phase from amorphous matrix. The precipitation of quasicrystalline phase with a large volume fraction in the Zr₆₄Ni₇Nb₃Cu₁₆Al₁₀ alloy indicates that the decrease of Ni content promotes the formation of icosahedral phase. Johnson-Mehl-Avrami analysis of isothermal transformation data suggests that the icosahedral phase precipitation proceeds by a diffusion-controlled growth mode with nearly constant nucleation rate. Furthermore, the Zr_71−xNi_xNb₃Cu₁₆Al₁₀ (x=7, 9, 11 at%) alloys possess high glass-forming ability, and the critical diameter for glass formation reaching 6 mm, 9 mm and 9 mm by copper-mould casting method, respectively.