Physics of Metallic Glasses and Amorphous Solids. Stronger than steel or ...
glasses are ideal materials for everything from cell-phone cases to aircraft parts.
Physics of Metallic Glasses and Amorphous Solids
Stronger than steel or titanium -- and just as tough -- metallic glasses are ideal materials for everything from cell-phone cases to aircraft parts. Replacing crystalline metals in the core of transformers, they can reduce significantly the energy losses. Typically, core loss can be 70%-80% less than with traditional crystalline materials, reducing the generation requirement, and when using electric power generated from fossil fuels, less CO2 emissions. Thus metallic glass cores in transformers has been widely adopted by large developing countries such as China and India where energy conservation and CO2 emission reduction have been put on priority. The energy savings are simply enormous--just these two countries can potentially save 25-30 TWh electricity annually, eliminate 6-8 GW generation investment, and reduce 20-30 million tons of CO2 emission by fully utilizing this new technology. Bulk metallic glasses are however sensitive to fatigue, leading to shear bands and breakage that limits their usefulness.
Shear Band Failure in a Metallic Glass Sample
Our research addresses this very issue. These materials are amorphous, and have exciting mechanical properties. For example the stress-strain curves 0.65 0.55
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Stress Strain Curves at IncreasingTemperatures for Amorphous Solids show clear evidence of plastic instabilities. In previous published work we have developed many of both the massively parallel simulational methods, as well as Hessian matrix approaches needed to study such instabilities.
Comparison of Simulations and Theory for the Flow Fields Near Plastic Events in Nonmagnetic Amorphous Solids Using these methods we have been able to identify in quasistatic athermal simulations several key preliminary results including how plastic events first
appear in amorphous elastic media and show that it involves generic saddlenode instabilities. We have also studied the transition to both ductile flow and shearbanding in nonmagnetic amorphous solids as functions of how interatomic potential behaves at large separations; the scaling of nonlinear elastic coefficients with system size; the density of low-lying plastic modes (these control the transition to plastic response) in both the `elastic' and `ductile' branch of the strained material
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Simulations and Theory for Shearbanding in Amorphous Solids Amorphous solids and metallic glasses also have important magnetic properties that show avalanches and magnetic instabilities. Together with Professor Itamar Procaccia at the Weizmann Institute we are combining massively parallel simulations of metallic glasses under the combined effects of strain and magnetic fields with new approaches to the analysis of the raw data so generated. We are especially interested in the development of new Hessian matrix methods combining both spatial and spin degrees of freedom whose eigenvalues tell us about the stability of different modes to failure, and whose eigenfunctions tell us about the spatial and magnetic structure of these modes. This will allow us to identify the types of local plastic events and local magnetic domain structures that develop in amorphous solids and
metallic glasses as well as their stability under the combined application of externally applied strain and changing magnetic fields.
Left: Hysteresis Curves for a Bulk Metallic Glass. Right : An Avalanche as a Magnetic Domain Looses Stability Important questions concern how the chemical composition, and the resulting interatomic and magnetic potentials interact in magnetic amorphous solids in order to control their material properties including plasticity and soft or hard magnetic behavior. Using these techniques we propose to examine questions of magnetoplasticity and magnetostriction in metallic glasses including how strain influences magnetic domain structure, size distribution and magnetic orientation.
RECENT PUBLICATIONS ON AMORPHOUS SOLIDS AND METALLIC GLASSES 1.
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Lerner, Edan; Procaccia, Itamar; Ching, Emily S. C.; Hentschel, H. G. E. Relations between material mechanical parameters and interparticle potential in amorphous solids, PRB 79, 180203 (2009). H. G. E. Hentschel, Smarajit Karmakar, Edan Lerner, Itamar Procaccia, Size of plastic events in strained amorphous solids at finite temperature, Phys. Rev. Lett. 104, 025501 (2010).
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Laurent Boue, H.G.E Hentschel, Itamar Procaccia, Ido Regev and Jaques Zylberg, Effective temperature in elastoplasticity of amorphous solids, Phys. Rev. B 81, 100201 (2010).
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H. G. E. Hentschel, Smarajit Karmakar, Edan Lerner, Itamar Procaccia, Do Athermal Amorphous Solids Exist? Phys. Rev. E 83, 061101 (2011).
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H. George E. Hentschel, Valery Ilyin, Itamar Procaccia, The plastic response of magnetoelastic amorphous solids. EPL 99 26003(2012). ArXiv: arXiv:1203.4055
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Ratul Dasgupta, H. George E. Hentschel and Itamar Procaccia, Microscopic Mechanism of Shear Bands in Amorphous Solids , Phys.Rev. Lett.,109 25502 (2012). Supplementary material. arXiv: arXiv:1207.3591
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Ratul Dasgupta, H. George E. Hentschel and Itamar Procaccia, The YieldStrain in Shear Banding Amorphous Solids, Phys. Rev. E, 87, 022810 (2013). ArXiv: arXiv:1208.3333.
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Ratul Dasgupta, Ashwin Joy, H.G.E.Hentschel and Itamar Procaccia, Derivation of the Johnson-Samwer T^(2/3) Temperature Dependence of the Yield Strain in Metallic Glasses, Phys. Rev. B 87, 020101(R) (2013). ArXiv: arXiv:1210.7982.
