Atomic structure of Mg-based metallic glass investigated with neutron diffraction, reverse Monte Carlo modeling and electron microscopy.

Rafał Babilas,Laszlo Temleitner,Dariusz Łukowiec

doi:10.3762/bjnano.8.119

Rafał Babilas, Laszlo Temleitner + Show 1 more

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https://doi.org/10.3762/bjnano.8.119

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Abstract

The structure of a multicomponent metallic glass, Mg65Cu20Y10Ni5, was investigated by the combined methods of neutron diffraction (ND), reverse Monte Carlo modeling (RMC) and high-resolution transmission electron microscopy (HRTEM). The RMC method, based on the results of ND measurements, was used to develop a realistic structure model of a quaternary alloy in a glassy state. The calculated model consists of a random packing structure of atoms in which some ordered regions can be indicated. The amorphous structure was also described by peak values of partial pair correlation functions and coordination numbers, which illustrated some types of cluster packing. The N = 9 clusters correspond to the tri-capped trigonal prisms, which are one of Bernal’s canonical clusters, and atomic clusters with N = 6 and N = 12 are suitable for octahedral and icosahedral atomic configurations. The nanocrystalline character of the alloy after annealing was also studied by HRTEM. The selected HRTEM images of the nanocrystalline regions were also processed by inverse Fourier transform analysis. The high-angle annular dark-ﬁeld (HAADF) technique was used to determine phase separation in the studied glass after heat treatment. The HAADF mode allows for the observation of randomly distributed, dark contrast regions of about 4–6 nm. The interplanar spacing identified for the orthorhombic Mg2Cu crystalline phase is similar to the value of the first coordination shell radius from the short-range order.

Highlights

Magnesium-based metallic glasses are often described as the most sought after alloys given the increasing demand for light weight and low cost materials with good functional properties [1,2,3]
A set of advanced experimental methods, including the neutron diffraction, reverse Monte Carlo modeling and high-resolution electron microscopy were used to characterize the atomic structure of multicomponent, Mg65Cu20Y10Ni5 alloy in a glassy and postannealed state
A combination of the methods was very useful to describe the local atomic structure of the studied alloy in the glassy state and after structural transformation formed by heat treatment

Summary

Introduction

Magnesium-based metallic glasses are often described as the most sought after alloys given the increasing demand for light weight and low cost materials with good functional properties [1,2,3]. Many chemical compositions of metallic glasses based on. The structural characterization of Mg-based metallic glasses are less described and studied. Some works on the structural characterization have been conducted by investigating the ternary Mg–Cu–Y glasses. Gao et al [11] performed ab initio molecular dynamics simulations of the structural evolution of a Mg65Cu25Y10 alloy from liquid to glass state. Laws et al [12] provided an analysis of the dynamic crystallization in Mg65Cu25Y10 bulk metallic glass using transmission electron microscopy and atom probe tomography. Detailed information on the atomic configuration of the multicomponent Mg-based glassy alloys is not often reported

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