Structural Irreversibility in Enhanced Brittleness under Fatigue in Zr-Based Amorphous Solids

Published

December 19, 2012

Author(s)

Peng Tong, Despina Louca, Gongyao Wang, Peter K. Liaw, Yoshihiko Yokoyama, Anna Llobet, Hiroshi Kawaji, Yiming Qiu, Yunfeng Shi

Abstract

Amorphous metals are solid metallic materials devoid of periodicity, with disordered atomic structures achieved by supercooling the viscous liquid to avoid crystallization. Whilst trapped in this supercooled state with an atomic topology that resembles that of a liquid¹, amorphous alloys exhibit unique properties that could have a widespread industrial impact. Thus, how they mechanically respond and deform under applied stress is vital to their functionality. Typically, metallic glasses have undesirably low ductility and most commonly plastically deform through shear bands^2-4. However, the aforementioned shear bands are markedly absent under fatigue testing, and with no other apparent atomistic signature, the role of the structure and its dynamics are still poorly understood. Here, we show that fragile behavior is enhanced in glasses under fatigue in part due to shrinkage of loosely bonded regions. By combining neutron diffraction, inelastic scattering and specific heat, C_p, measurements, we observe a drastic local atomic rearrangement that is hysteretic in temperature and scales with the compression frequency. Associated with this is a softening in the dynamics envisaged in the so-called Boson peak where not one but two collective excitations are observed corresponding to two kinds of localized oscillators that may be a signature of strong glass formers. The suppression of the two excitations under fatigue indicates a decrease in the number of soft-like regions of loosely bound atoms that renders the glass more fragile.

Citation

Metals

Volume

2

Pub Type

Journals

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Keywords

metallic glass, fatigue, neutron scattering

Citation

Tong, P. , Louca, D. , Wang, G. , Liaw, P. , Yokoyama, Y. , Llobet, A. , Kawaji, H. , Qiu, Y. and Shi, Y. (2012), Structural Irreversibility in Enhanced Brittleness under Fatigue in Zr-Based Amorphous Solids, Metals, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=908876 (Accessed July 26, 2024)