| Abstract Scope |
Structural changes in a Zr-Cu-Ni-Al bulk glass-forming, relatively "strong", liquid alloy on cooling from above the equilibrium liquidus temperature studied by synchrotron radiation X-ray diffraction and first-principles molecular dynamics (MD) simulation are compared with those of a "fragile" Pd-Cu-Ni-P one. According to the results chemical ordering forming Zr-Cu,Ni, Zr-Al and Zr-Zr atomic pairs takes place in the Zr-Cu-Ni-Al supercooled liquid alloy on cooling. However, here the change in the Zr-Cu,Ni peak area to other peaks area ratio is smaller than in case of the Pd-Cu-Ni-P alloy (Cu,Ni-P to other peaks ratio) in accordance with a lower fragility index of the Zr-Cu-Ni-Al melt. It indicates that fragility is a sign of instability of short and medium range order in fragile liquids. The atomic structure of a Ni-Nb bulk metallic glass was studied by means of ultra high vacuum scanning tunneling microscopy. Direct atomic structure observation was supported by MD simulation. |