[en] Highly ductile Zr₆₅Al_7.5Cu_27.5 bulk metallic glass (BMG) containing nanometer scaled fcc phase was obtained by copper mold casting. Room temperature compression tests revealed superior mechanical properties of the alloy: yielding stress of 1670 MPa, Young's modulus of 90 GPa, elastic strain of 2%, and especially a remarkable plasticity of over 50%. The marginal BMG is a useful model system to examine the nanocrystal coalescence model and the shear-transformation-zone model proposed for large scale plastic deformations of metallic glasses

[en] Metallic elements having negative enthalpies of mixing tend to form characteristic local atomic clusters. In this review, we use the structural information in the first nearest neighbour shell level, or first-shell atomic cluster, to derive the composition rules of two types of complex alloy phases, quasicrystals and bulk metallic glasses, both being composed of elements with negative enthalpies of mixing. We first show the composition phenomena in quasicrystal-forming systems, where major composition rules such as cluster line, electron concentration and atomic size criteria are derived. Then we analyse the composition rules of bulk metallic glasses using the very same approaches. Finally, we summarize their common composition rules into more general rules and basic theories. (topical review)

[en] This paper analyzes the structure and composition characteristics of ternary quasicrystals and bulk metalic glasses from the viewpoint of atomic clusters. It is pointed out that quasicrystals and bulk metallic glasses satisfy a cluster line rule. The cluster line refers to a straight composition line linking a specific cluster to the third element in a ternary alloy phase diagram. A ternary quasicrystal or bulk metallic glass composition is located at the intersection point of two cluster lines. Ternary quasicrystal and bulk metallic glass compositions can be the expressed with a cluster-plus-glue-atom model which can predict new ternary bulk metallic glasses

[en] Bulk metallic glass formations in Co-based alloy systems are investigated with the guidance of our cluster line approach and minor-alloying principle. Basic ternary alloy compositions in Co-B-Si system are first determined by cluster lines defined by linking special binary clusters to third elements. Then these basic ternary alloys are further minor-alloyed with 4-5 at. % Nb and bulk metallic glasses of 3 mm in diameter are formed in (Co₈B₃-Si)-Nb, Co₈B₃ being dense-packed cluster. The bulk metallic glasses are expressed approximately with a unified simple composition formula: (Co₈B₃)₁(Si,Nb)₁. Finally a quantity of Fe substitution for Co further improves the glass-forming abilities and these Co-Fe-based quinary bulk metallic glasses have good soft magnetic properties with high saturation magnetization I_s, up to 0.98T, and low coercive force H_c, below 6 A/m