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Hydrogen-induced enhancement of thermal stability in VZr(H) metallic glasses
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.ORCID iD: 0000-0001-7367-1196
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.ORCID iD: 0000-0001-5397-7753
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2022 (English)In: Materialia, E-ISSN 2589-1529, Vol. 24, article id 101496Article in journal (Refereed) Published
Abstract [en]

Prediction of crystallization temperatures in metallic glasses is still an open question. Investigations of multi component alloys are common in the literature, however, binary and ternary alloys are more suitable for funda-mental studies due to their simplicity. Here, we show that a low thermodynamic driving force for crystallization can be associated with a high crystallization temperature. The driving force is determined by calculating - for the first time in metallic glasses - the temperature dependent Gibbs free energies of the alloys using ab initio density functional theory, in combination with the stochastic quenching method. The crystallization tempera-tures of VxZr100-x and VxZr67-xH33 have been determined using simultaneous in-situ x-ray scattering techniques and resistivity measurements. The onset of crystallization is found to exhibit a parabolic dependence throughout the composition range, whereas alloying with hydrogen increases the thermal stability up to 150 K close to the amorphous-crystalline boundaries. These findings suggest that hydrogen acts as an alloying element with the ability to dynamically tune the intrinsic properties of the material. Lastly, temperature-dependent descriptions of the Gibbs free energy and kinetic considerations of a metallic glass are necessary for a complete characterization of the crystallization process.

Place, publisher, year, edition, pages
2022. Vol. 24, article id 101496
National Category
Condensed Matter Physics Materials Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-468122DOI: 10.1016/j.mtla.2022.101496ISI: 000841222700001OAI: oai:DiVA.org:uu-468122DiVA, id: diva2:1639227
Funder
Swedish Research Council, 2018-05200Swedish Energy Agency, 2020-005212Swedish Research Council, 2018-05973Carl Tryggers foundation , CTS 17:350Carl Tryggers foundation , CTS 19:272Available from: 2022-02-20 Created: 2022-02-20 Last updated: 2024-03-21Bibliographically approved
In thesis
1. Designing metallic glasses: Alloying, properties, and degrees of freedom
Open this publication in new window or tab >>Designing metallic glasses: Alloying, properties, and degrees of freedom
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present design rules for metallic glasses with respect to glass formation, thermal stability (resistance to crystallisation), and material properties can still be improved. A main design rule is to use thermodynamic calculations to determine the composition of eutectic points in the phase space. The work in this thesis shows that thermodynamic calculations can be utilised to a larger extent than calculating liquidus temperatures. To gain additional insight about metallic glass forming alloys, they are herein classified into systems with a small and large negative enthalpy of mixing of the liquid. The mixing enthalpy influences the number of compound phases (intermetallic or ceramic) forming at equilibrium. A small negative enthalpy of mixing results in few compound phases at equilibrium, whereby the formation range of metallic glasses is dominated by the atomic size mismatch, for instance in ZrNbCrMo and VZr. A low thermal stability is observed for glasses with a chemical composition close to the amorphous-to-crystalline boundary if the alloys have a small negative enthalpy of mixing. Moreover, thermodynamic calculations are herein used to relate the crystallisation temperature to the thermodynamic driving force for crystallisation. A lower thermodynamic driving force in VZrH metallic glasses is related to a higher crystallisation temperature, where the configurational entropy is found to have a stabilising effect. The thermodynamic phase equilibrium is used to identify where the constituent atoms separate or mix in an alloy, which influences glass formation, thermal stability, and material properties. However, a negative enthalpy of mixing of the liquid can be misleading since the chemical interactions between the constituents in the solid state can nonetheless be repulsive. This is seen in the VZr and TaNiSiC metallic glasses investigated herein. There the enthalpy in the liquid and solid have opposite signs, whereby separation tendencies are observed in the solid amorphous state. The separation tendencies can result in variations in the local chemical composition on the nanometer scale and possibly larger length scales. The variations are found to be the origin of reduced thermal stability and corrosion resistance in TaNiC glasses. Furthermore, the occurrence of the variations may also lead to a larger extent of hydrogen embrittlement in metallic glasses.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2022. p. 84
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2123
Keywords
amorphous alloys, enthalpy of mixing, glass formation, thermal stability, thermodynamics, mechanical properties, corrosion resistance, hydrogen
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-468123 (URN)978-91-513-1424-2 (ISBN)
Public defence
2022-04-08, Siegbahnsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research , GMT14-0048
Available from: 2022-03-17 Created: 2022-02-20 Last updated: 2022-04-05
2. The interaction of hydrogen with metallic glass
Open this publication in new window or tab >>The interaction of hydrogen with metallic glass
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Combining theoretical ab initio calculations with high-purity thin film sample synthesis and in situ measurements is a compelling way to bridge the gap in our understanding concerning hydrogen in metallic glasses, which is the primary work of this dissertation thesis. The main emphasis has been on how hydrogen affects the structure of metallic glasses, and how those changes influence not only the electronic properties of the amorphous metals but also their thermal stability.    

The real-space correlations in the form of the pair distribution functions in thin metallic films have primarily only been accessible through synchrotron radiation. An effective methodological procedure using laboratory-based x-ray sources is here brought forth, which, for the first time, can produce accessible and accurate pair distribution functions from thin films down to a thickness of 80 nm.    

The underpinning mechanisms behind the hydrogen-induced volume expansion of metallic glasses in the form of the dipole force tensor and an elastic hydrogen-hydrogen interaction were examined using in situ neutron reflectometry and first-principles calculations of expanding V80Zr20 amorphous structures. The dipole force tensor was concluded to be similar in magnitude to a mole-fraction-weighted sum of the ones found in hydrogen-contained vanadium and zirconium crystals, and the theoretical calculations demonstrated that it and the interaction energy varies with hydrogen concentration.   

The electronic structure of the metallic glass V80Zr20 was determined via hard x-ray photoemission spectrometry and confirmed by first-principles calculations to be modified by the presence of hydrogen, in which a collection of s-d hybridized states 7 eV below the Fermi level was formed. The changes closer to the Fermi level, together with the volume expansion, were via experiments and ab initio calculations established to cause a parabolic change in resistance and a strong wavelength dependence on the optical transmission.   

The thermal stability of amorphous VxZr1-x metals, investigated via ab initio calculations of the thermodynamic driving force towards crystallization, was found to affirm the observed hydrogen-induced enhancement in thermal stability. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2024. p. 82
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2376
Keywords
metallic glass, hydrogen, thin film, density functional theory, stochastic quenching, molecular dynamics, x-ray diffraction, pair distribution function, neutron reflectometry, volume expansion, elastic hydrogen-hydrogen interaction, dipole force tensor, electronic structure, optical conductivity, resistivity, optical transmission, x-ray photoelectron spectroscopy, thermodynamic driving force, Gibbs free energy
National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-525370 (URN)978-91-513-2075-5 (ISBN)
Public defence
2024-05-16, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2024-04-19 Created: 2024-03-21 Last updated: 2024-04-19

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Kaplan, MaciejBylin, JohanMalinovskis, PauliusScheicher, Ralph H.Pálsson, Gunnar K.

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