Nano icosahedral quasicrystals in Zr-based glassy alloys

摘要

A nanoscale icosahedral quasicrystalline phase formation was found by the slight deviation from the three-component rule for high glass-forming ability in a Zr_(65)Al_(7.5)Ni_(10)Cu_(17.5) glassy alloy. Since the primary phase consists of fcc Zr_2Ni and I-phases in the Zr_(65)Al_(7.5)Ni_(10)Cu_(16.5) (Ag, Pd, Au or Pt)_1 glassy alloys, where an icosahedron is contained in both the phases, it is suggested that the local icosahedral atomic configuration exists in the glassy state and it stabilizes the supercooled liquid state. We also clarified that an I-phase precipitates in the Zr_(70)Cu_(29)Pd_1 and Zr_(70)Ni_(20)Al_9Pd_1 glassy alloys and no I-phase formation is observed in the Zr_(70)Ni_(29)Pd_1 amorphous alloy. Since the supercooled liquid region is confirmed in the Zr_(70)Cu_(30) and Zr_(70)Ni_(20)A1_(10) glassy alloys and is not observed in the Zr_(70)Ni_(29) amorphous alloy, it is concluded that the stability of the supercooled liquid state is strongly correlated with the existence of the local icosahedral order.