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

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.

Influence of Dielectric Screenings on Phonon Frequencies and Acoustic Properties of Pd-Based Bulk Metallic Glasses

“…However, the understanding of phonon dynamics and atomic structure configuration are essential for understanding their mechanical and thermal properties [6][7][8][9]. The phonon dynamics of metallic glasses have been studied experimentally [10][11] using neutron scattering. Theoretically computed phonon frequencies have been investigated by many researchers [12][13][14][15][16][17] for correlating them with mechanical and thermal properties in a variety of metallic glasses.…”

“…The value of β and δ can be determined using equations (8), (9), (10) and (11). The sound velocities for both Pd 40 Ni 10 Cu 30 P 20 and Pd 64 Ni 16 P 20 BMGs are estimated for the longitudinal mode ( with different dielectric screenings and transverse mode ( ) in the long wavelength region from the respective dispersion curves.…”

“…For the Pd 40 Ni 10 Cu 30 P 20 BMG, the experimental values of , and [2] are 172.60×10 9 Nm -2 , 35.50×10 9 Nm -2 and 9.259×10 3 kgm -3 respectively and for the Pd 64 Ni 16 P 20 BMG, the experimental values of , and [2,17] are taken as 172.00×10 9 Nm -2 , 32.80×10 9 Nm -2 and 10.08×10 3 kgm -3 respectively. The values of is calculated using the , the values of the respective force constants β and δ for both the BMGs are obtained by substituting the respective values of , and κ e in equations (8), (9), (10) and (11). Hence all the input parameters for computing phonon dispersion curves for both the BMGs are known and are listed in Table 1.…”

Phonon Dynamics and Acoustic and Thermodynamic Properties of Pt_57.5Cu_14.7Ni_5.3P_22.5 Bulk Metallic Glass

“…The understanding of phonon dynamics and micro-structural configuration of metallic glasses is essential for understanding their acoustic, elastic and thermal properties [2][3][4][5][6][7]. Experimentally, neutron scattering has been used to study the phonon frequencies of metallic glasses [8,9]. The theoretically computed phonon dispersion curves both for longitudinal and transverse modes have also been reported by computer simulation and recursion techniques [8][9][10][11][12][13] for a variety of metallic glasses.…”

“…Experimentally, neutron scattering has been used to study the phonon frequencies of metallic glasses [8,9]. The theoretically computed phonon dispersion curves both for longitudinal and transverse modes have also been reported by computer simulation and recursion techniques [8][9][10][11][12][13] for a variety of metallic glasses. Three main theoretical approaches, namely Hubbard and Beeby [14], Takeno and Goda [15] and that of Bhatia and Singh [4] are widely used for computing phonon frequencies of metallic glasses.…”