Microdomain atomic structure of Zr50Pd40Al10 metallic glasses and its formation mechanism

Zr-based Zr50Pd40Al10 metallic glasses has not only crystalline phases of about 5 nm in diameter but also amorphous phases. In this work, the radial distribution functions (RDFs) of amorphous structure of Zr(50)Pd(40)Al(10 )metallic glasses were firstly measured by electron diffraction, and then Reverse Monte Carlo (RMC) optimization accompanied by density functional theory (DFT) calculations. The amorphous structure has not only short-range order but also good medium-range order. In the RDFs of its amorphous structure, the first and the second peaks are located at 2.96 angstrom and 4.79 angstrom, respectively. Partial radical distribution functions (PRDFs) show that the contributions of the first and the second nearest-neighbor distances of various atom pairs to the G(r) peak values, and the first nearest-neighbor distances of Pd-Zr and Zr-Zr atom pairs are the sources of main G(r) peak values between 2 angstrom and 6 angstrom. The competition mechanism for generating the Zr25Pd55Al20 amorphous phase and the intermetallic crystalline phase Pd11Zr9 is associated with the differences of atomic radius, the proportion, and the melting point of different atoms, as well as the heat of mixing between atoms, leading to an equilibrium state of the two phases. Accordingly, a composite system with intertwined nanocrystals and amorphous phases is in turn formed, and improves the stability of the material. (C) 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.