A topological approach to design Ni-based bulk metallic glasses with high corrosion resistance
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A topological approach to design Ni-based bulk metallic glasses with high corrosion resistance A.P. Wang and J.Q. Wanga) Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, People’s Republic of China (Received 7 July 2006; accepted 18 September 2006)
The structural model for metallic glasses and the topological instability criterion for multicomponent alloy systems have been combined to formulate a design protocol for bulk metallic glasses (BMGs). New Ni-Nb-Zr bulk metallic glasses with high corrosion resistance have been discovered. The experimental results in literature also support the use of this approach as a practically efficient method to select bulk metallic glass-forming compositions.
Bulk metallic glasses (BMGs) with unusual combinations of physical, chemical, and mechanical properties are promising candidates for applications.1,2 A number of BMGs with high glass forming ability (GFA) have been developed.1–6 In the case of Ni-based alloys, BMG rods up to 3∼5 mm in diameter using Cu mold casting, have been achieved in the muliti-component Ni-Nb-Ti-Zr-CoCu,7 Ni-Zr-Ti-Si-Sn,8 Ni-Nb-Sn,9 and Ni-Cu-Ti-Zr-Al10 systems. These Ni-based BMGs have been reported to exhibit a high strength of 3.8 GPa,9 high thermal stability, and high corrosion resistance.11 Since the discovery of amorphous alloys, a variety of criteria has been proposed to predict alloy compositions with better GFA. Among them, Trg,12 three empirical rules,2 and the ␥ criterion13 are the most often used. Although these methods give useful directions, the development of new BMGs is still a very time-consuming process. Therefore, finding more specific guidelines for locating easy glass-forming alloys would be of great significance. Recently, Miracle et al.14,15 analyzed the atomic size distributions of multicomponent amorphous alloys with different GFA, and proposed a structural model16 for metallic glasses based on the efficient face-centered cubic (fcc) dense packing of clusters. This structural model contains only four topologically distinct atomic constituents: solvent atoms ⍀, the primary cluster-forming solutes ␣, secondary solutes , and tertiary solutes ␥. The a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2007.0020 J. Mater. Res., Vol. 22, No. 1, Jan 2007
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convention chosen is that the largest solutes are ␣ atoms, and  and ␥ solutes are progressively smaller. Atomic radii within ±2% of one another are considered topologically equivalent. It has been used to predict metallic glass compositions for Zr- and Ca-based BMGs and some other ordinary amorphous alloys. To extend the model to Ni-based BMGs, we examine the simple ternary alloy system of NicNiNbcNbSncSn.9 According to Miracle’s structural model, Ni is the ⍀ atom, and Sn and Nb occupy the ␣ and  sites, respectively. Therefore, Ra =
RSn 0.16200 = 1.300 = RNi 0.12459
,
R =
RNb 0.14290 = 1.147 = RNi 0.12459
.
an
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