Tensile properties of glassy MgZnCa wires and reliability analysis using Weibull statistics Bruno Zberg, Edward R. Arata, Peter J. Uggowitzer, Jo ¨rg F. Lo ¨ffler * Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland Received 26 February 2009; accepted 19 March 2009 Abstract Mg-based metallic glass wires were produced via the melt-extraction technique. Their mechanical properties were evaluated by carrying out tensile tests on electrochemically polished dogbone-shaped wire samples, and their reliability was estimated using Weibull analysis. The wires exhibit a tensile strength of 675–894 MPa with a characteristic strength of 817 MPa and a Weibull modulus of 20.6. The high Weibull modulus is explained by the plastic behavior and necking of the tensile samples. The tensile tests also reveal an extended amount of homo- geneous plastic deformation, which can be assigned to the circular geometry and flawless surface quality of the specimens. Ó 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Metallic glasses; Fibers; Magnesium alloys; Tensile tests; Weibull statistics 1. Introduction Crystalline magnesium alloys exhibit a high specific strength at very low density and are therefore an interesting material for lightweight applications. A significant increase in yield strength can be achieved for Mg-based glasses: the absence of a dislocation-based plastic deformation mecha- nism in metallic glasses generates a yield strength which is 2–3 times larger than that of their crystalline counterparts, and an elastic limit of about 2% compared to 0.5% for crys- talline alloys [1–3]. However, most metallic glasses show limited plasticity, as their plastic deformation occurs via the formation of shear bands [1]. In bending, thick metallic glass plates fail after the initiation of a single shear band, while glasses with a thickness below a critical size show significant bending plasticity due to the initiation of multiple shear bands [4]. In fact, plastic strain to fracture increases with decreasing sample dimension, and brittle failure is no longer expected when the sample dimension is in the range of or below the plastic zone size d ¼ K 2 c =pr 2 , with K c the fracture tough- ness and r the yield strength [5]. As opposed to metallic or oxide glasses, glassy polymers extend nonuniformly in tensile tests via shear banding or necking after some initial homogeneous deformation [6]. There, the initiation of shear bands depends on the geometrical flaws which pro- duce non-symmetric conditions. These can, however, be suppressed to some degree by the use of special, axis-sym- metric tensile samples [6]. The metallic glass wires in this study exhibit a high axial symmetry, which may increase the probability of homoge- neous deformation before shear bands are initiated. These wires may therefore demonstrate increased flexibility and possibly even some ductility in tension. In addition, the tensile strength of thin fibers increases with decreasing diameter, independent of whether they are made of oxide glasses or crystalline or amorphous metals [7–9]. The com- bination of high strength, increased flexibility, potential ductility and low density thus makes Mg-based glassy wires an interesting candidate for lightweight applications if the reliability of the material is sufficient. This study investigates the mechanical properties of glassy Mg-based wires and their reliability by means of Weibull analysis. Such analysis has so far been applied 1359-6454/$36.00 Ó 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.actamat.2009.03.028 * Corresponding author. Tel.: +41 44 632 25 65; fax: +41 44 633 14 21. E-mail address: joerg.loeffler@mat.ethz.ch (J.F. Lo ¨ ffler). www.elsevier.com/locate/actamat Available online at www.sciencedirect.com Acta Materialia xxx (2009) xxx–xxx ARTICLE IN PRESS Please cite this article in press as: Zberg B et al. Tensile properties of glassy MgZnCa wires and reliability analysis using Weibull sta- tistics. Acta Mater (2009) doi:10.1016/j.actamat.2009.03.028