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      Local melting to design strong and plastically deformable bulk metallic glass composites

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          Abstract

          Recently, CuZr-based bulk metallic glass (BMG) composites reinforced by the TRIP (transformation-induced plasticity) effect have been explored in attempt to accomplish an optimal of trade-off between strength and ductility. However, the design of such BMG composites with advanced mechanical properties still remains a big challenge for materials engineering. In this work, we proposed a technique of instantaneously and locally arc-melting BMG plate to artificially induce the precipitation of B2 crystals in the glassy matrix and then to tune mechanical properties. Through adjusting local melting process parameters (i.e. input powers, local melting positions, and distances between the electrode and amorphous plate), the size, volume fraction, and distribution of B2 crystals were well tailored and the corresponding formation mechanism was clearly clarified. The resultant BMG composites exhibit large compressive plasticity and high strength together with obvious work-hardening ability. This compelling approach could be of great significance for the steady development of metastable CuZr-based alloys with excellent mechanical properties.

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          Most cited references67

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          Characterization of supercooled liquid Ge2Sb2Te5 and its crystallization by ultrafast-heating calorimetry.

          Differential scanning calorimetry (DSC) is widely used to study the stability of amorphous solids, characterizing the kinetics of crystallization close to the glass-transition temperature T(g). We apply ultrafast DSC to the phase-change material Ge(2)Sb(2)Te(5) (GST) and show that if the range of heating rates is extended to more than 10(4) K s(-1), the analysis can cover a wider temperature range, up to the point where the crystal growth rate approaches its maximum. The growth rates that can be characterized are some four orders of magnitude higher than in conventional DSC, reaching values relevant for the application of GST as a data-storage medium. The kinetic coefficient for crystal growth has a strongly non-Arrhenius temperature dependence, revealing that supercooled liquid GST has a high fragility. Near T(g) there is evidence for decoupling of the crystal-growth kinetics from viscous flow, matching the behaviour for a fragile liquid suggested by studies on oxide and organic systems.
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            Transformation-mediated ductility in CuZr-based bulk metallic glasses.

            Bulk metallic glasses (BMGs) generally fail in a brittle manner under uniaxial, quasistatic loading at room temperature. The lack of plastic strain is a consequence of shear softening, a phenomenon that originates from shear-induced dilation that causes plastic strain to be highly localized in shear bands. So far, significant tensile ductility has been reported only for microscopic samples of around 100 nm (ref. 4) as well as for high strain rates, and so far no mechanisms are known, which could lead to work hardening and ductility in quasistatic tension in macroscopic BMG samples. In the present work we developed CuZr-based BMGs, which polymorphically precipitate nanocrystals during tensile deformation and subsequently these nanocrystals undergo twinning. The formation of such structural heterogeneities hampers shear band generation and results in macroscopically detectable plastic strain and work hardening. The precipitation of nanocrystals and their subsequent twinning can be understood in terms of a deformation-induced softening of the instantaneous shear modulus. This unique deformation mechanism is believed to be not just limited to CuZr-based BMGs but also to promote ductility in other BMGs.
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              Bulk metallic glass composites with transformation-mediated work-hardening and ductility.

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                Author and article information

                Journal
                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group
                2045-2322
                13 February 2017
                2017
                : 7
                : 42518
                Affiliations
                [1 ]School of Mechanical, Electrical & Information Engineering, Shandong University (Weihai) , Wenhua Xilu 180, 264209 Weihai, P.R. China
                [2 ]Centre for Advanced Structural Materials, Department of Mechanical and Biomedical Engineering, City University of Hong Kong , 999077 Hong Kong SAR, P.R. China
                [3 ]Laboratory for Microstructures, Shanghai University , 200444 Shanghai, P.R. China
                [4 ]IFW Dresden, Institute for Complex Materials , Helmholtzstraße 20, 01069 Dresden, Germany
                [5 ]Erich Schmid Institute of Materials Science, Austrian Academy of Sciences , Jahnstraße 12, A-8700 Leoben, Austria
                [6 ]Department Materials Physics, Montanuniversität Leoben , Jahnstraße 12, A-8700 Leoben, Austria
                Author notes
                Article
                srep42518
                10.1038/srep42518
                5304197
                28211890
                1787b4dc-8026-4625-b6fe-2f09f52ef3e4
                Copyright © 2017, The Author(s)

                This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

                History
                : 12 September 2016
                : 13 January 2017
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