Formation of an icosahedral quasicrystalline phase in Zr₆₅Al_7.5Ni₁₀M_17.5 (M = Pd, Au or Pt) alloys

An icosahedral (I) phase was found to be formed as a metastable phase in the crystallization process of amorphous Zr₆₅Al_7.5Ni₁₀M_17.5 (M = Pd, Au or Pt) alloys. The three amorphous alloys show an endothermic reaction due to the glass transition, followed by two exothermic peaks. The first exothermic peak is due to the precipitation of an I-phase and the second one results from the transition from the I to crystalline mixed phases of Zr₄Al₃ + Zr₂Ni + Zr₂Pd (Zr₂Au or ZrPt). The I-phase consists of fine grains with a size of about 10 nm no distinct residual amorphous phase is seen. The formation of the I-phase in the new Zr-based alloy systems with a large supercooled liquid region and high glass-forming ability is important for the future development of bulk quasicrystalline alloys as basic science and engineering materials.