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Effect of Ni-substitution on glass forming ability, mechanical, and magnetic properties of FeBNbY bulk metallic glasses
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.ORCID iD: 0000-0003-2170-0076
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.ORCID iD: 0000-0003-4889-4210
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
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2013 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 1, 013505- p.Article in journal (Refereed) Published
Abstract [en]

We present a method to identify bulk glass forming ability by partial substitution of Fe by Ni in FeBNbY based amorphous alloy ribbons and as a consequence obtain enhanced mechanical and soft magnetic properties of bulk glassy rods of diameter as large as 4.5 mm. A detailed investigation of thermal, mechanical, and magnetic properties of (Fe0.72-x NixB0.24Nb0.04)(95.5)Y-4.5 alloys (with x similar to 0.02, 0.04, 0.06, 0.08, 0.1) was carried out. The supercooled regime (Delta T-x) and other glass forming parameters, e. g., reduced glass transition temperature (T-rg), the gamma (gamma) parameter, etc., were found to be enhanced due to the Ni substitution resulting in improvement of glass forming ability (GFA). The maximum values of such parameters (Delta T-x similar to 94 K, T-rg similar to 0.644, and gamma similar to 0.435) were obtained for the alloy with x similar to 0.06, making it possible to cast cylindrical rods with 4.5 mm diameter for this composition. Nanoindentation studies on glassy rods also point out that (Fe0.66Ni0.06B0.24Nb0.04)(95.5)Y-4.5 alloy exhibit the maximum value of hardness (H similar to 12 GPa) as well as elastic modulus (E similar to 193 GPa) among all of these samples. In addition to these, that particular sample shows the lowest room temperature coercivity (H-c similar to 210 mOe). By annealing at 823 K, H-c can be further reduced to 60 mOe due to its structural relaxation. We attribute the improved soft magnetic and mechanical properties of as-quenched (Fe0.66Ni0.06B0.24Nb0.04)(95.5)Y-4.5 alloy to higher packing density attained due to its large glass forming ability.

Place, publisher, year, edition, pages
2013. Vol. 113, no 1, 013505- p.
Keyword [en]
Alloys, Amorphous alloys, Magnetic properties, Mechanical properties, Niobium
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-101835DOI: 10.1063/1.4772753ISI: 000313329000022Scopus ID: 2-s2.0-84872089597OAI: oai:DiVA.org:kth-101835DiVA: diva2:549758
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Vinnova
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QC 20120906. Updated from manuscript to article in journal.

Available from: 2012-09-06 Created: 2012-09-05 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Functional Metallic Glasses
Open this publication in new window or tab >>Functional Metallic Glasses
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

For decades, Metallic Glass, with its isotropic featureless structure while exhibiting outstanding mechanical properties was possible only at a high rate of quenching and with at least one dimension in the submicron regime.  This limitation was overcome with the discovery of Bulk Metallic glasses, BMGs, containing three or more elements following the additional two empirical rules of optimum geometric size differences and negative energy of mixing among the constituent elements. Since then thousands of Fe-, Ni-, Al-, Mg-, Ti- based BMGs have been discovered and comprehensively investigated mainly by groups in Japan and USA. Yet the discovery of new combinations of elements for BMGs is alchemy. We do not know with certainty which element when added will make possible a transition from being a ribbon to a bulk rod.

   In this thesis we report a discovery of castable BMGs rods on substitution of Fe by nickel in an alloy of FeBNb which could otherwise have been only melt-spun into ribbons.  For example, we find that substitution of just 6 at.% of Fe raises the glass forming range, GFA, to as much as ∆Tx =40K while the other parameters for GFA like Trg, γ, and δ reach enhanced values 0.57, 0.38, and 1.40 respectively.  Furthermore, the electrical conductivity is found to increase by almost a factor of two.  Magnetically it becomes softer with coercivity 260mOe which further reduces to much lower values on stress relaxation.  Ni does not seem to carry a magnetic moment while it enhances the magnetic transition temperature linearly with Ni concentration. We have investigated the role of Ni in another more stable BMGs based FeBNbY system in which case ∆Tx becomes as large as 94K with comparable enhancement in the other GFA parameters. Due to the exceptional soft magnetic properties, Fe-based bulk metallic glasses are considered potential candidate for their use in energy transferring devices. Thus the effect of Ni substitution on bulk forming ability, magnetic and electrical transport properties have been studied for FeBNb and FeBNbY alloy systems. The role of Ni in these systems is densification of the atomic structure and its consequence.

We have exploited the superior mechanical properties of BMGs by fabricating structures that are thin and sustainable.  We have therefore investigated studies on the thin films of these materials retaining their excellent mechanical properties. Magnetic properties of FeBNb alloy were investigated in thin films form (~200-400nm) in the temperature range of 5-300K. These Pulsed Laser deposited amorphous films exhibit soft magnetism at room temperature, a characteristic of amorphous metals, while they reveal a shift in hysteresis loop (exchange anisotropy, HEB=18-25Oe), at liquid helium temperature. When thickness of films is reduced to few nanometers (~8-11nm), they exhibit high transparency (>60%) in optical spectrum and show appreciably high saturation Faraday rotation (12o/μm, λ= 611nm). Thin films (~200-400nm) of Ni substituted alloy (FeNiBNb) reveal spontaneous perpendicular magnetization at room temperature. Spin-reorientation transition was observed as a function of film thickness (25-400nm) and temperature (200-300K), and correlated to the order/disorder of ferromagnetic amorphous matrix as a function of temperature. These two phase films exhibits increased value of coercivity, magnetic hardening, below 25K and attributed to the spin glass state of the system.

   Using the bulk and thin films we have developed prototypes of sensors, current meters and such simple devices although not discussed in this Thesis.                                     

   Ti-based bulk metallic glasses have been attracting significant attention due to their lower density and high specific strength from structural application point of view. High mechanical strength, lower values of young’s modulus, high yield strength along with excellent chemical behaviors of toxic free (Ni, Al, Be) Ti-based glassy metals make them attractive for biomedical applications. In the present work, toxic free Ti-Zr-Cu-Pd-Sn alloys were studied to optimize their bulk forming ability and we successfully developed glassy rods of at least 14mm diameter by Cu-mold casting. Along with high glass forming ability, as-casted BMGs exhibit excellent plasticity. One of the studied alloy (Ti41.5Zr10Cu35Pd11Sn2.5) exhibits distinct plasticity under uniaxial compression tests (12.63%) with strain hardening before failure which is not commonly seen in monolithic bulk metallic glasses.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xiv, 60 p.
Keyword
Bulk Metallic glasses, glass forming ability, soft magnetism, thin films, magnetic properties, magnetic hardening, plasticity, biocompatibility
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-101901 (URN)978-91-7501-476-0 (ISBN)
Public defence
2012-09-21, V2, Teknikringen 76, 2tr, Stockholm, 14:00 (English)
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Hero-m
Note

QC 20120906

Available from: 2012-09-06 Created: 2012-09-05 Last updated: 2012-09-19Bibliographically approved

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Ström, ValterBelova, Lyubov

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