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Title: Theoretical prediction and experimental confirmation of devitrification pathways in the Zr 2Cu 1-xPd x Metallic Glass System

Abstract

Using a model amorphous alloy series, Zr{sub 2}Cu{sub 1-x}Pd{sub x} (x = 0, 0.25, 0.5, 0.75 and 1), we demonstrate that ab initio calculations can predict likely metastable phase formation during devitrification by comparing these with time-resolved X-ray scattering studies. All compositions share the same equilibrium C11{sub b} phase, yet they follow different devitrification pathways. Only x = 0.5 leads to a metastable C16 phase formation. This corresponds precisely to calculations showing the C16 phase is closest in energy to the stable C11{sub b} phase. The competition is shown to be dominated by electronic structure rather than size effects, with the favored composition for the C16 phase forming a pseudo-gap at the Fermi energy. All Pd-containing compounds devitrify first into a quasicrystalline phase. Zr{sub 2}Cu{sub 1-x}Pd{sub x} compounds based on the NiTi{sub 2} O{sub h}{sup 5} structure are higher in energy relative to the C16 and C11{sub b} structures for all compositions, and the calculations show no increase in stability with Pd concentration.

Authors:
 [1];  [2];  [1];  [3];  [1]
  1. ORNL
  2. Ames Laboratory and Iowa State University
  3. Iowa State University
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
932133
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Acta Materialia; Journal Volume: 55
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALLOYS; ELECTRONIC STRUCTURE; GLASS; SCATTERING; STABILITY; METALLIC GLASSES

Citation Formats

Xu, Min, Ye, Y. Y., Sordelet, Daniel J, Kramer, M. J., and Morris, James R. Theoretical prediction and experimental confirmation of devitrification pathways in the Zr2Cu1-xPdx Metallic Glass System. United States: N. p., 2007. Web.
Xu, Min, Ye, Y. Y., Sordelet, Daniel J, Kramer, M. J., & Morris, James R. Theoretical prediction and experimental confirmation of devitrification pathways in the Zr2Cu1-xPdx Metallic Glass System. United States.
Xu, Min, Ye, Y. Y., Sordelet, Daniel J, Kramer, M. J., and Morris, James R. Mon . "Theoretical prediction and experimental confirmation of devitrification pathways in the Zr2Cu1-xPdx Metallic Glass System". United States. doi:.
@article{osti_932133,
title = {Theoretical prediction and experimental confirmation of devitrification pathways in the Zr2Cu1-xPdx Metallic Glass System},
author = {Xu, Min and Ye, Y. Y. and Sordelet, Daniel J and Kramer, M. J. and Morris, James R},
abstractNote = {Using a model amorphous alloy series, Zr{sub 2}Cu{sub 1-x}Pd{sub x} (x = 0, 0.25, 0.5, 0.75 and 1), we demonstrate that ab initio calculations can predict likely metastable phase formation during devitrification by comparing these with time-resolved X-ray scattering studies. All compositions share the same equilibrium C11{sub b} phase, yet they follow different devitrification pathways. Only x = 0.5 leads to a metastable C16 phase formation. This corresponds precisely to calculations showing the C16 phase is closest in energy to the stable C11{sub b} phase. The competition is shown to be dominated by electronic structure rather than size effects, with the favored composition for the C16 phase forming a pseudo-gap at the Fermi energy. All Pd-containing compounds devitrify first into a quasicrystalline phase. Zr{sub 2}Cu{sub 1-x}Pd{sub x} compounds based on the NiTi{sub 2} O{sub h}{sup 5} structure are higher in energy relative to the C16 and C11{sub b} structures for all compositions, and the calculations show no increase in stability with Pd concentration.},
doi = {},
journal = {Acta Materialia},
number = ,
volume = 55,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • One interesting aspect of rretallic glasses is the numerous instances of the deviation of the phase selection from the amorphous state to thermodynamically stable phases during the crystallization process. Their devitrification pathways allow us to study the relationship between the original amorphous structure and their crystalline counter parts. Among the various factors of phase selections, size and electronic effects have been most extensively studied. Elucidating the phase selection process of a glassy alloy will be helpful to fill in the puzzle of the changes from disordered to ordered structures. In this thesis, Two model Zr 2Pd xCu 1-x and Zrmore » 2Ni xCu 1-x (x = 0, 0.25, 0.5, 0.75 and 1) glassy systems were investigated since: (1) All of the samples can be made into a homogenous metallic glass; (2) The atomic radii differ from Pd to Cu is by 11%, while Ni has nearly the identical atomic size compare to Cu. Moreover, Pd and Ni differ by only one valence electron from Cu. Thus, these systems are ideal to test the idea of the effects of electronic structure and size factors; (3) The small number of components in these pseudo binary systems readily lend themselves to theoretical modeling. Using high temperature X-ray diffraction (HTXRD) and thermal analysis, topological, size, electronic, bond and chemical distribution factors on crystallization selections in Zr 2Pd xCu 1-x and Zr 2Ni xCu 1-x metallic glass have been explored. All Zr 2Pd xCu 1-x compositions share the same Cu11b phase with different pathways of meta-stable, icosahedral quasicrystalline phase (i-phase), and C16 phase formations. The quasicrystal phase formation is topologically related to the increasing icosahedral short range order (SRO) with Pd content in Zr 2Pd xCu 1-x system. Meta-stable C16 phase is competitive with C11b phase at x = 0.5, which is dominated by electronic structure rather than size effects. Cu-rich and Ni-rich compositions in Zr 2Ni xCu 1-x trend to divitrify to C11b or C16 phases respectively. In the proposed pseudo binary phase diagram, the domain of C16, C11b and co-existence phases are mainly related with the topology in the amorphous structure and formation enthalpies of crystalline phases.« less
  • No abstract prepared.
  • Due to their scientific significance and potential engineering applications, bulk metallic glasses are among the most intensively studied advanced materials. Understanding the glass-forming ability (GFA) of these metallic alloys is a long-standing subject. While a large number of empirical factors have been proposed to correlate with GFA of the alloys, a full understanding of GFA remains a goal to achieve. Since glass formation is a competing process against crystallization, we have performed a systematic analysis on the crystallization kinetics of two known best metallic glass-formers Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20} (in at. %) and Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10}Be{sub 22.5}more » based on classical nucleation and growth theory. Our results show that there is a dramatic difference between the two alloys in their nucleation behavior although they possess comparable GFA. Particularly, an extremely sharp nucleation peak ({approx}10{sup 18}/m{sup 3} s) is found for Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20} around 632 K with a very small half maximum width of 42 K, implying that this alloy is an excellent candidate for nanocrystallization studies. Moreover, we have also found that the GFA of these alloys can be calculated to a high accuracy and precision based on the classical theory, suggesting that the classical theory may be sufficient to account for glass formation mechanism in these metallic alloys.« less
  • We have experimentally studied the electronic structures of ternary glassy metals of (Cu{sub 1{minus}{ital x}}Ni{sub {ital x}}){sub 33}Zr{sub 67}. The density of states at the Fermi level, {ital N}(0), has been estimated from measurements of the superconducting upper critical field. We have also measured the valence band, using x-ray photoemission spectroscopy. We found that the electronic structure is affected by the Ni concentration in ternary glassy metals of (Cu{sub 1{minus}{ital x}}Ni{sub {ital x}}){sub 33}Zr{sub 67}. Also discussed are relationships between the electronic structure and superconducting properties, detailed band structures including the bandwidth, the position of the subband, the intensity ofmore » spectrum, and various theoretical models.« less