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Basic polyhedral clusters have been derived from intermetallic compounds at near-eutectic composition by considering a dense packing and random arrangement of atoms at shell sites. Using such building units, bulk metallic glasses can be formed. This strategy was verified in the Cu–Zr binary system, where we have demonstrated the existence of Cu8Zr5 icosahedral clusters in Cu61.8Zr38.2, Cu64Zr36, and Cu64.5Zr35.5 amorphous alloys. Furthermore, ternary bulk metallic glasses can be developed by doping the basic Cu–Zr alloy with a minority element. This hypothesis was confirmed in systems (Cu0.618Zr0.382)100-xNbx, where x=1.5 and 2.5 at. %, and (Cu0.618Zr0.382)98Sn2. The present results may open a route to prepare amorphous alloys with improved glass forming ability. [ABSTRACT FROM AUTHOR]

Crystallization kinetics of a Zr[sub 46.8]Ti[sub 8.2]CU[sub 7.5]Ni[sub 10]Be[sub 27.5] bulk glass in the supercooled liquid region have been investigated by performing in situ high-temperature and high-pressure x-ray diffraction measurements using synchrotron radiation. A pressure-time-temperature-transformation diagram, describing the onset of crystallization as a function of time during isothermal annealing under pressure, is presented. Different pressure dependences of crystallization kinetics in the temperature range for the glass have been observed and further be explained by a model of competing processes of the thermodynamic potential barrier of nucleation and the diffusion activation energy under pressure. [ABSTRACT FROM AUTHOR]

Comments on the reversible phase transition between amorphous and crystalline in Zr[sub 41.2]Ti[sub 13.8]Cu[sub 12.5]Ni[sub 10]Be[sub 22.5] under high pressure at room temperature. Characterization of metallic glasses; Analysis of diffraction patterns in the transition; Demonstrations on pressure-induced crystallization of the glasses.

The pressure effect on the crystallization of the Al[sub 89]La[sub 6]Ni[sub 5] amorphous alloy has been investigated by in situ high-pressure and high-temperature x-ray powder diffraction using synchrotron radiation. The amorphous alloy crystallizes in two steps in the pressure range studied (0-4 GPa). The first process, corresponding to simultaneous precipitation of fcc-Al crystals and the metastable bcc-(AlNi)[sub 11]La[sub 3]-like phase, is governed by a eutectic reaction. The second process corresponds to the transformation of a residual amorphous alloy into fcc-Al, Al[sub 11]La[sub 3], Al[sub 3]Ni, and as yet unidentified phase(s). The applied pressure strongly affects the crystallization processes of the amorphous alloy. Both temperatures first decrease with pressure in the pressure range of 0-1 GPa and then increase with pressure up to 4 GPa. The results are discussed with reference to competing processes between the thermodynamic potential barrier and the diffusion activation energy under pressure. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]