Effect of Al on Local Structures of Zr–Ni and Zr–Cu Metallic Glasses

Abstract

In order to investigate the role of Al on the thermal stability of supercooled liquid state, the local structures of Zr 70 M 30 and Zr 70 M 20 Al 10 (M ¼ Ni, Cu) metallic glasses have been studied by the X-ray diffraction and EXAFS measurements. It is found that the different effect of Al substitution on the local structures around Cu and Ni elements is exhibited. No characteristic change is observed in the local structure in the ZrCu metallic glass by Al substitution, whereas a drastic change in the environment around Ni atom can be confirmed in the Zr-Ni metallic glass. That is, the coordination number of Zr around Ni decreases significantly by substitution of Al in the Zr-Ni metallic glass. This would be caused by the preferential correlation between Al and Zr. This result suggests that Al plays a dominant role on the formation of novel local structure with a decomposition of the tetragonal Zr 2 Ni-like local environment in the Zr-Ni binary alloy. We conclude that the novel local structure contributes to the stability of the supercooled liquid state in the Zr-Al-Ni metallic glass.

Atomic structure in Zr70Ni30 metallic glass

“…In addition, three experimental data ͑XRD and Zr and Ni K-edge EXAFS͒ were simultaneously used for RMC simulation in the present work. The reliability to uncover complex atomic structure of Zr 70 Ni 30 MG, thus, might be higher than those, in which only one XRD data 8 or one neutron ͑elec-tron͒ diffraction data 15,16 was used ͑Table I͒. We further compared the atomic structure of Zr 70 Ni 30 MG with possible intermetallic ZrNi compounds, as shown in Fig.…”

“…8 Thus, studies of atomic structure in such simple MGs are strongly demanded, which will promote our understanding to multicomponent bulk metallic glasses. However, structure of Zr-Ni MGs is still not completely understood [15][16][17][18] in spite of its wide amorphous-forming compositional range. 19 In the present work, we report the atomic structure of a Zr 70 Ni 30 MG by reverse Monte Carlo ͑RMC͒ simulation combining with x-ray diffraction ͑XRD͒ and extended x-ray absorption of fine structure ͑EXAFS͒ as well as Voronoi tessellation method.…”

Local Structure Study in Zr-Based Metallic Glasses

“…5. The calculated results of the tetragonal Zr 2 Cu structure and icosahedral cluster model defined by the atomic distances obtained from parameter fitting results by RDF measurement 17) of the Zr K-edge and Cu K-edge are also shown in Fig. 5.…”

The Development of Structure Model in Metallic Glasses

“…Detailed structure information of metallic glasses can be generally inferred by the following two approaches: (1) Experiments such as X-ray diffraction (XRD) 28,29 , extended X-ray absorption of fine structure (EXAFS) [30][31][32] , small-angle X-ray scattering (SAXS) 33 ; atom probe tomography 34 , high-resolution transmission electron microscope (HREM) [35][36][37] , synchrotron diffraction 38,39 and neutron scattering 40 , (2) Computer simulation such as Monte Carlo simulation 41 , Reverse Monte Carlo (RMC) simulation 42,43 , Ab initio Molecular Dynamics (AIMD) simulation 44,45 and molecular dynamics (MD) simulation 46 . Based on the experiments and computer simulations, several structural models for the amorphous alloys have been proposed and successfully used to describe characteristics of metallic glasses from different perspectives.…”