Glass formation, thermal properties, and elastic constants of La-Al-Co alloys
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n Li and Tao Zhang Department of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
Ju¨rgen Eckertb) Institute for Complex Materials, IFW Dresden, D-01171 Dresden, Germany; and Institute of Materials Science, TU Dresden, D-01062 Dresden, Germany (Received 29 January 2010; accepted 24 March 2010)
The compositional dependence of glass formation and thermal and elastic properties was clarified for the ternary La–Al–Co bulk glass-forming system. The existing linear correlation between La concentration and characteristic temperatures, i.e., the glass transition temperature Tg and the onset temperature of crystallization Tx, as well as the elastic moduli in this system can give a useful guideline for the chemical design of desirable bulk metallic glasses (BMGs) with tunable physical properties in advance. The relationship between Tg and elastic constants for the La–Al–Co BMGs can be quantitatively described using a microscopic model proposed by T. Egami.
I. INTRODUCTION
As one of the most fascinating advanced metallic materials developed half a century ago, metallic glasses (MGs) have been widely used for a variety of applications, such as antitheft labels and highly efficient magnetic transformers, heads of golf clubs and for tennis racquets in sport instruments, and luxury goods.1–3 However, the nature of the structure and the glass transition of MGs is still not very well understood because of the absence of well-defined translational crystallographic symmetry in this kind of materials.4 Therefore, searching for possible relationships between chemical compositions, glass-forming ability (GFA), and properties of MGs is imperative to design or select desirable MGs from a large number of candidates. So far, many quantitative rules have been advocated to predict the GFA correlated with composition and thermal properties.5–22 These criteria can be divided into three types. One is based on the criteria related to the thermal behaviors of the material, e.g., the criterion of the reduced glass transition temperature Trg (Trg ¼ Tg/Tl, where Tg and Tl are the glass-transition and the liquidus temperatures) 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.2010.0177 1398
http://journals.cambridge.org
J. Mater. Res., Vol. 25, No. 7, Jul 2010 Downloaded: 10 Apr 2015
proposed by Turnbull, the role of the width of the supercooled liquid range DTx (DTx ¼ Tx Tg, where Tx are the onset temperature of crystallization) by Inoue, or the g parameter [g ¼ Tx/(Tg þ Tl)] by Lu et al., etc.5–8 These thermal parameters showing a good quantitative correlation with the GFA in many glass-forming systems have been widely used to obtain bulk metallic glasses (BMGs). Secondly, some methodologies based on thermodynamic models were proposed
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