Chuang Dong

Bulk metallic glasses formed by alloying the Cu6Zr5 cluster

The bulk metallic glass formation in the Cu-Zr-M ternary systems by alloying of a binary basic Cu6Zr5 cluster was investigated, where M stands for Sn, Mo, Ta, Nb, Ag, Al and Ti. The Cu6Zr5 cluster is a capped Archimedean antiprism that characterizes the local structure of the Cu10Zr7 crystalline phase. This cluster composition almost superposes with Cu-Zr eutectic Cu0.56Zr0.44. A series of alloys along the cluster line (Cu6Zr5)(1-x)M-x were examined for their glass forming abilities. Alloy rods with a diameter of 3 mm were prepared by copper mould suction casting method and analyzed by XRD and thermal analysis. The Cu-Zr based bulk metallic glasses were discovered with minor Nb, Sn, Mo, Ta additions (<= 2at%) and Al, Ti, Ag (8at%<= concentration <= 9at%). The alloying mechanism was discussed in the light of atomic size, cluster-linking structure and electron concentration factors.

A cluster line approach for composition rules of quasicrystals and bulk metallic glasses

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.

Cluster-based composition rules for ternary alloy systems

The cluster-based composition rule in ternary alloy systems including quasicrystals, bulk metallic glasses, crystalline phases and Lave phases-related body-centered cubic (BCC) solid solution forming systems was summarized. The so-called cluster line in a ternary phase diagram refers to a straight composition line linking a specific binary cluster to the third element. The composition ranges of quasicrystals and bulk metallic glasses can be determined by the direct use of cluster lines, where two cluster lines intersect at the optimum phase forming composition. Furthermore, the alloys on the cluster line in Laves phase-related BCC solid solution alloy systems have larger hydrogen storage capacities.

Glass formation of ternary Sin-based Sm-AI-Co bulk metallic glasses

Abstract Ternary Sm-based Sm-AI-Co alloys at specific compositions designed using an e/a - and cluster-related criteria exhibit high glass forming abilities and form bulk glassy rods of 3 mm in diameter by a copper mold suction-casting method. Four compositions of bulk metallic glasses (BMGs) are Sm 50 Al 25 Co 25 , Sm 52 Al 24 Co 24 , Sm 54 Al 23 Co 23 and Sm 56 Al 22 Co 22 , which all satisfy a constant conduction electron concentration of 1.5. Among them, the BMG exhibiting the largest reduced glass transition temperature ( T rg ) is Sm 50 Al 25 Co 25 , which reaches 0.648. The glass transition temperature T g and the onset crystallization temperature T x of this alloy are respectively 579 and 640 K at a heating rate of 20 K/min.

A cluster line approach to finding new Fe-B-Y-Nb-Zr bulk metallic glasses

The glass forming ability of the [(Fe12/13Y1/13)(100-x)B-x](96)Nb2Zr2 (x=9-26) system was investigated using a series of cluster lines. Three types of clusters, an icosahedron (Fe12Y), a capped Archimedes anti-prism (Fe8B3) and a capped trigonal prism (Fe9B), as well as a binary eutectic (Fe83B17) were considered. Bulk glassy alloy rods of 3 mm in diameter were synthesized using a copper mold suction-casting method. The glass transition temperature was observed for. all samples in the boron range of 15.9at%-25.7at%, with the alloy at 15.9at% of boron having the best thermal properties. The ferrous-based bulk metallic glasses (BMG) obtained have high reduced glass transition temperatures with the maximum reaching 0.63 and large supercooled liquid regions with the maximum reaching 111 K. Magnetic testing revealed a large value of coercive force and remanent magnetization, being 11 kA/m and 0.1 T, respectively.

Cluster-based composition rule for Laves phase-related BCC solid solution hydrogen storage alloys

A new cluster line approach for the composition rule of Laves phase-related BCC solid solution hydrogen-storage alloys was presented. The cluster line in a ternary phase diagram refers to a straight composition line linking a specific binary cluster to the third element. In the Laves phase-related BCC solid solution alloy system such as Ti-Cr-V, Ti-Cr tends to form binary Cr2Ti Laves phase while Ti-V and Cr-V to form solid solutions. This Laves phase is characterized by a close-packing icosahedral cluster Cr7Ti6. A cluster line Cr7Ti6-V is then constructed in this system. Alloy rods with a diameter of 3 mm of compositions along this line were prepared by copper-mould suction method. The alloy structure is found to vary with the V contents. Furthermore, the P-C-T measurements indicate that the cluster-line (Cr7Ti6)1-xVx alloys have large hydrogen storage capacities.