Propagation of shear bands in a Cu 47.5 Zr 47.5 Al 5 bulk metallic glass
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J. Das and M.H. Lee Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Institute for Complex Materials, Dresden D-01171, Germany
S. Yi Department of Materials Sciences and Metallurgy, Kyungpook National University, Buk-gu, Daegu 702-701, Korea
E. Fleury Advanced Metals Research Center, Korea Institute of Sciences and Technology, Cheongryang, Seoul 130-650, South Korea
Z.F. Zhang Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
W.H. Wang Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
J. Eckertb) Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Institute for Complex Materials, Dresden D-01171, Germany (Received 3 May 2007; accepted 8 October 2007)
We report a novel finding of slither propagation of shear bands on the fracture surface of a Cu47.5Zr47.5Al5 bulk metallic glass (BMG). The nanoscale heterogeneities in the as-cast state are aggregated along shear bands with irregular morphology. Such heterogeneities create a fluctuating stress field during shear band propagation leading to a slither propagation mode. The slither propagation of 10 to 15 nm wide shear bands is effective to improve both the plasticity and the “work-hardening-like” behavior of BMGs if the size, the morphology, and the elastic properties of the heterogeneities are intimately intercalated during solidification.
I. INTRODUCTION
Bulk metallic glasses (BMGs) usually undergo inhomogeneous plastic deformation at room temperature with very limited macroscopic plastic strain.1–4 The plastic flow allows only a few shear bands to be active, causing catastrophic failure of the sample.1–4 This disadvantage of BMGs creates a significant difficulty for its use in industrial applications. The recent development of unique BMGs, so-called ductile BMGs, overcoming this a)
Address all correspondence to this author. e-mail: [email protected] b) This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http:// www.mrs.org/jmr_policy. DOI: 10.1557/JMR.2008.0025 6
J. Mater. Res., Vol. 23, No. 1, Jan 2008 http://journals.cambridge.org Downloaded: 14 Mar 2015
disadvantage, has been highlighted in several publications.5–10 Consequently, it is an urgent issue to understand the deformation mechanisms of these ductile BMGs. So far, there are two major trends attempting to solve the deformation mechanisms operating in ductile BMGs: the first approach considers the elastic constants of the material,7,9,11 and the second one focuses on microstructural heterogeneities.5,6,8,10,12 The flow of metallic glass-forming liquids, and the flow and fracture of metallic glasses and their relation to elastic constants, i.e., Poisson’s ratio , have been used to determine the ductility or brittleness of BMGs.7,11 Similarly, the intrinsic plasticity and brittleness of BMGs have also been correlated with the ra
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