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W.R. Chen Department of Mechanical Engineering, Dalian University, Dalian 116622, China

J. Wu, J.B. Qiang, and Y.M. Wang State Key Laboratory of Materials Modification, Dalian University of Technology, Dalian 116024, China

C. Donga) State Key Laboratory of Materials Modification, Dalian University of Technology, Dalian 116024, China; and International Center for Materials Physics, Chinese Academy of Sciences, Shenyang 110016, China (Received 11 September 2007; accepted 28 November 2007)

Bulk metallic glass (BMG) formations in Co- and Fe-based alloy systems are investigated by using our cluster line approach in combination with minor alloying principle. Basic ternary alloy compositions in Co–B–Si, Fe–B–Y, and Fe–B–Si systems are first determined by cluster lines defined by linking special binary clusters to third elements. Then the basic ternary alloys are further minor alloyed with 3 to 5 at.% Nb to improve glass-forming abilities (GFAs) and ␾3 mm BMGs are formed in (Co8B3–Si)–Nb and (Fe8B3–Y)–Nb but not in (Fe8B3–Si)–Nb, TM8B3 (TM ⳱ Fe, Co) being the most compact binary cluster. The BMGs are expressed approximately with a unified simple composition formula: (TM8B3)1M1, M ⳱ (Si, Nb) or (Y, Nb). Finally, mutual Fe and Co substitutions further improve the GFAs as well as the soft magnetic properties, e.g., Is reaching 0.98 T and Hc < 6 A/m for the Co–Fe–B–Si–Nb BMGs. Using the (cluster)1(glue atom)1 model, a new ternary BMG Fe8B3Nb1 is obtained.

I. INTRODUCTION

Fe-based and Co-based bulk metallic glasses (BMGs) are drawing increasing attention because of their superior mechanical and soft magnetic properties.1–4 However, compared with Pd-, Zr-, and Cu-based BMGs,5 the Feand Co-based BMGs have relatively weak glass-forming abilities (GFAs) and are formed only in multicomponent systems with narrow composition ranges, generally containing more than three constituents (except a few ternary systems such as Fe–B–Y, which can form BMG rods with a diameter of 2 mm6,7). There have been extensive efforts in developing composition rules such as Inoue’s criteria,5 confusion principle,8 and eutectic rule.9 In our previous work,10–15 we have proposed a new cluster line approach for the composition design of ternary quasicrystals and Zr-, Cu-, and rare earth (RE)-

II. COMPOSITION DESIGN USING CLUSTER LINE AND MINOR ALLOYING

a)

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2008.0210 J. Mater. Res., Vol. 23, No. 6, Jun 2008

http://journals.cambridge.org

based BMGs. In addition, it was well known that minor alloying by elements with atomic sizes different from the main constituent elements could dramatically improve GFAs.16 For example, minor alloying of Cu–Zr BMGs by Nb, Sn, and Mo significantly improves their GFAs.11 In this paper, we will combine the cluster line approach with the minor-alloying principle to design Fe- and Cobased BMGs with large GFAs. The alloy design procedure is the following. First, basic ternary alloy compositions in Co–B–Si, Fe–B–Y, and Fe–B–Si systems are resp