Local chemical and topological order in Al-Tb and its role in controlling nanocrystal formation

Date

2012-02-01

Author

Kalay, Yunus Eren
HWANG, Jinwoo
VOYLES, P. M.
KRAMER, M. J.

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

160
views

0
downloads

How the chemical and topological short- to medium-range order develops in Al-Tb glass and its ultimate effect on the control of the high number density of face-centered-cubic-Al (fcc-Al) nuclei during devitrification are described. A combined study using high-energy X-ray diffraction (HEXRD), atom probe tomography (APT), transmission electron microscopy and fluctuation electron microscopy (FEM) was conducted in order to resolve the local structure in amorphous Al90Tb10. Reverse Monte Carlo simulations and Voronoi tessellation analysis based on HEXRD experiments revealed a high coordination of Al around Tb atoms in both liquid and amorphous states. APT results show Al-rich and Al-depleted regions within the as-quenched alloy. A network structure of Tb-rich clusters divides the matrix into nanoscale regions where Al-rich clusters are isolated. It is this finely divided network which allows the amorphous structure to form. Al-rich regions are the locus for fcc-Al crystallization, which occurs before the intermetallic crystallization. FEM reveals medium-range ordered regions similar to 2 nm in diameter, consistent with fcc-Al and trigonal-like Al3Tb crystal structures. We propose that the high coordination of Al around Tb limits diffusion in the intermetallic network, allowing for the isolated Al-rich regions to form at high density. These regions are responsible for the extremely high density of Al nanocrystal nuclei. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Subject Keywords

Nanocrystalline materials, Crystallization, Scanning/transmission electron microscopy (STEM), Three-dimensional atom probe (3DAP), X-ray diffraction (XRD)

URI

https://hdl.handle.net/11511/33091

Journal

ACTA MATERIALIA

DOI

https://doi.org/10.1016/j.actamat.2011.11.008

Collections

Department of Metallurgical and Materials Engineering, Article

Suggestions

OpenMETU
Core

Angle of graph energy - A spectral measure of resemblance of isomeric molecules Gutman, I; Türker, Burhan Lemi (2003-11-01) A method, elaborated earlier by one of the present authors, for measuring the structural resemblance of isomeric alternant conjugated hydrocarbons, based on a graph-spectral quantity theta, called the angle of total pi-electron energy approach has been extended now to arbitrary molecules. Some general properties of theta have been established.
Local atomic structure in al-re marginal metallic glasses Övün, Mert; Kalay, Yunus Eren; Department of Metallurgical and Materials Engineering (2016) Partial devitrification of the Al-RE marginal metallic glasses results in anomalous nucleation rate of nanocrystals conflicting with the classical nucleation theory by several orders of magnitude. One of the theoretical approaches explaining this phenomenon is the medium-range order (MRO) structures within the range of 1-2 nm that may be present both in the quenched amorphous state and its liquid precursor. In this work, these structures have been investigated conducting both experimental methods such as hi...
Composition dependence of lattice parameters and band gap energies of thallium based layered mixed crystals Hasanlı, Nızamı (2015-07-01) Compositional dependence of lattice parameters and unit cell volumes of TlMeX2-type (Me = Ga or In and X = S or Se) layered mixed crystals with monoclinic structure has been studied by X-ray diffraction technique. It is revealed that the lattice parameters of TlGa1-xInxSe2, TlGa(S1-xSex)(2), TlGa1-xInxS2 and TlIn(Se1-xSx)(2) mixed crystals increase due to the substitution of gallium atoms by indium and sulfur atoms by selenium. Moreover, the absorption edges of these mixed crystals have been investigated th...
Nanocrystallization in marginal glass forming alloys Demirtaş, Tuba; Kalay, Yunus Eren; Department of Metallurgical and Materials Engineering (2013) The marginal glass-forming alloys have attracted much attention due to unique products of devitrification with a very high number density of nuclei up to 10^23 m^-3. Among these alloy systems, utmost interest is given to Al-RE and Al-TM-RE alloys with excellent lightweight mechanical (fracture strength close to 1 GPa) and chemical properties attributed to the presence of an extremely high density of nanocrystals embedded in an amorphous matrix. Classical nucleation theory fails in explaining this abnormal n...
Terahertz spectroscopy of dicyanobenzenes: Anomalous absorption intensities and spectral calculations Esentürk, Okan; Heilweil, E. J. (2007-07-06) Terahertz absorption spectra of three isomeric structures of dicyanobenzene in chloroform solution and solid phase at 298 K are reported. These spectra exhibit enhanced absorption in low THz range compared to most organic systems because of strong coupling to phonon modes. Molecular vibrational spectral calculations show strong correlation with the experiment especially for solution spectra. All intramolecular modes were assigned and intermolecular modes identified. Out-of-plane intramolecular modes at low ...

Citation Formats

Y. E. Kalay, J. HWANG, P. M. VOYLES, and M. J. KRAMER, “Local chemical and topological order in Al-Tb and its role in controlling nanocrystal formation,” ACTA MATERIALIA, pp. 994–1003, 2012, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/33091.