Precipitation of icosahedral quasicrystalline and crystalline approximant phases in Zr–Cu–(Co, Rh or Ir) metallic glasses

Abstract Zr 70 Cu 30 , Zr 70 Cu 20 Co 10 , Zr 70 Cu 20 Rh 10 and Zr 70 Cu 20 Ir 10 glassy alloys were prepared by the single roller melt-spinning method and the crystallization process was studied by differential scanning calorimetry, X-ray diffraction and transmission electron microscopy, with an emphasis on the initial stage. The Zr 70 Cu 30 metallic glass crystallizes through the direct precipitation of the stable crystalline phase from the matrix. The addition of Co, Rh and Ir to the Zr 70 Cu 30 metallic glass induces the precipitation of metastable phases prior to the formation of the stable ones. The metastable phases are a Ti 2 Ni-type compound for Zr 70 Cu 20 Co 10 , a mixture of the Ti 2 Ni-type compound and an icosahedral quasicrystalline phase (I-phase) for Zr 70 Cu 20 Rh 10 , and the I-phase for Zr 70 Cu 20 Ir 10 metallic glasses. The different effects of Co, Rh and Ir addition are explained based on their difference in atomic radius.