This paper reports the atom probe analysis results of the oxygen dissolved in the as-cast amorphous and crystallized Zr65Cu15Al10Pd10 and Zr65Cul17.5Ni10Al17.5 alloys. Impurity oxygen ranging from 0.1 to 1 at.% is dissolved uniformly in the as-quenched Zr65Cu15A110Pd10 and Zr65Cu17.5Ni10Al7.5 amorphous alloys even though the oxygen is not added intentionally. When the Zr65Cu15Al10Pd10 alloy is crystallized, oxygen redistribution occurs; it is rejected from the primary Zr2 (Cu, Pd) crystals and partitioned in the subsequently crystallized phases. Oxygen atoms are enriched in some of the crystalline phases up to approximately 4 at.%, and virtually no oxygen is dissolved in the remaining amorphous phase. In the partially crystallized Zr65Cu17.5Ni10Al7.5 alloy, fine oxygen enriched particles containing ∼ 15 at.%O have been detected in direct contacted with crystalline grains. This work demonstrates that oxygen redistribution occurs during the crystallization reaction, thereby influencing the kinetics of crystallization.

An atom probe field ion microscope and 3-dimensional atom probe characterization of the solute distribution in a bulk Pd40Ni40P20 metallic glass in the as-cast state and after annealing has been performed. Statistical analysis of the atom probe atom-by-atom data detected the presence of short range ordering in the as-cast alloy. Phase separation at the nanometer level is observed in glassy samples after annealing above the glass-transition temperature. Crystallization proceeds by phase separation into three distinct crystalline phases. Atom probe analysis of the alloy annealed for 1 h at 410°C revealed that the primary nickel phosphide phase contained significant levels of palladium, the palladium-rich Pd3P phosphide phase contained low levels of nickel and there was a small amount of a palladium-nickel solid solution.

Electron energy loss spectroscopy (EELS) is used to extract information on the topological arrangement of atoms around Pd in the bulk-glass-forming Pd60Ni20P20. It is found that the environment around Pd in the glass is only a slight modification of the Pd crystalline structure. However, the modification is enough to allow this alloy to form a glass in bulk. In examining the differences between the structure of crystalline Pd and glassy Pd60Ni20P20 it is concluded that incorporation of Ni and P into the structure frustrates the structure enough that glass formation becomes easy.

Atomic volume effects in amorphous alloys obtained by rapid solidification and in bulk glasses are briefly reviewed. It is recalled that at high undercoolings, the release at the growth fronts, of the volume corresponding to the reduction of the molar volume upon solidification can sharply accelerate crystal growth in the melt through viscosity reduction. A method is then proposed for estimating the volume of mixing ΔVmix which is negative for elemental additions to glass-forming liquid alloy. It is argued that negative ΔVmix reduces atomic mobility in easy glass-forming alloys thus allowing the suppression during cooling, of nucleation and growth of crystallites. The ZrCuNi system is used as an example for applying this reasoning. It is shown that Al or Ti addition to ZrNiCu alloys lead to strongly negative ΔVmix and expected sharp drops in diffusion-controlled crystal growth kinetics in the melt.

The feasibility of using extended energy-loss fine structure (EXELFS) obtained from ∼1 nm regions of metallic glasses to study their short-range order has been examined. Ionization edges of the metallic glasses in the electron energy-loss spectrum (EELS) have been obtained from PdNiP bulk metallic glass and Ni2P polycrystalline powder in a transmission electron microscope. The complexity of EXELFS analysis of L- and M-ionization edges of heavy elements (Z>22, i.e. Ni and Pd) is addressed by theoretical caluculations using an ab initio computer code, and its results are compared with the experimental data.

Molecular dynamics simulation of the metallic glasses has been done. The embedded atom method potential function for copper is used to express the atomic interaction. The stress distribution in the glassy state is evaluated from specific volume occupied by single atom and local density in divided cells. The displacements of individual atom under the shear stress are calculated and the correlation between the displacements and the atomic volumes are investigated.

Recently, we have parametrized Sutton-Chen type empirical many body force fields for FCC transition metals to study the thermodynamic, mechanical, transport and phase behavior of metals and their alloys. We have utilized these potentials in lattice dynamics calculations and molecular dynamics simulations to describe the structure, thermodynamic, mechanical and transport properties of pure metals and binary alloys in solid, liquid and glass phases. Here, we will describe these applications: mechanical properties of binary alloys (Pt - Rh) and viscosity of a binary alloy, (Au - Cu), as a function of composition, temperature, and shear rate, crystal-liquid, liquid-crystal phase transformation in (Ni - Cu), liquid to glass transformation in a model glass former, (Ag - Cu).

This study is mainly devoted to the establisment of relations between easy glass forming ability of some multicomponent liquid alloys and strong heteroatomic bonding in connection with nucleation. The chemical short range order in typical liquid bulk glass formers as Zr-Ni-AI is evaluated from a statistical model and presented as Cowley's order parameters versus concentration. The effect of the nature and of the number of components on the chemical contribution to the liquid-crystal interface energy and on the Gibbs energy of crystallisation is analysed and discussed. A specific mechanism of nucleation based on a distribution of concentration fluctuations in the undercooled liquid is proposed. This homophase fluctuation mechanism, which is thermodynamically and kinetically justified, leads to a lower preexponential factor in the expression of the frequency of nucleation as a function of the number of components. Furthermore, this frequency of nucleation can be strongly lowered by an augmentation of the energy barrier of nucleation depending on the nature and the number of components in the liquid phase.

The viscosity of liquid lanthanum-based and aluminum-based La-Al-Ni alloys has been measured by an oscillating crucible method of the inverse suspending type in the temperature range from melting temperature (Tm) up to about 1400 K. In the case of La55Al45-xNix (x = 10∼40 at. %) alloys, the viscosity increased with increasing Ni content up to about 20 at. % Ni and then decreased with increasing the Ni content, while the activation energy for viscous flow decreased to a minimum value at about 20 at. % Ni. This composition is well consistent with that of the La-Al-Ni alloy having largest glass-forming ability.

Atomic structures of an amorphous La55A125Ni20 alloy in the supercooled liquid state have been investigated by in-situ electron diffraction using a specimen-heating stage in TEM and the imaging-plate intensity recording. From the analysis of atomic pair distribution functions, changes in interatomic distances and coordination numbers were clearly observed at temperatures in the supercooled liquid state. From the reverse Monte Carlo simulations, structural units (icosahedral, Archimedean anti-prism and trigonal prism atomic clusters) typical of the metallic glass structure were found and increased in the supercooled liquid region. In addition, the deformation behavior was investigated using tensile test. The superplastic elongation was confirmed at optimum strain rates in the supercooled liquid region. From the TEM observation of tensile tested specimens with superplastic elongation, β-La (fcc) nano precipitates in the amorphous matrix were confirmed. The superplasticity in this alloy is thought to originate in viscous flow due to the glassy structure formation but is closely related to an additional flow mode with the microcrystalline precipitation from the amorphous state during the deformation.

Volume changes in Zr46.7Ti8.3Cu7.5Ni10Be27.5 and Zr 65Al7.5Ni10Cu17.5 bulk metallic glasses have been observed by positron annihilation and density measurements. At low cooling rates excess volume of the order of 0.1 % is quenched in both glasses. Isothermal relaxation kinetics below the glass transition temperature obey a Kohlrausch law with exponents of β≈(0.3 ± 0.1). Structural relaxation is not accompanied by embrittlement, as indicated by simple mechanical tests. The outer surface plays a crucial role in annealing of excess volume, which can be restored by annealing above Tg. The observed free volume changes are at variance with the behavior of a perfectly strong glass. The temperature dependence of the positron lifetime is discussed in terms of thermal detrapping from shallow traps.

Improvement of glass forming ability (GFA) of two soft magnetic amorphous alloys (Fe75.5Ni1 3Si8.6B13.5 and Co69.6Fe1.3Mn4.5Si14.3B9 3Mo1) by heat treatment of melts prepared from different precursors (bulk ingot, rapidly quenched ribbons and granules) was studied. An assumption that the maximum undercooling ability corresponds to the maximum GFA was used to optimize the heat treatment mode. A temperature range was found by DTA for each alloy melt, favoring its undercooling (so called “undercoolable melt”). Usage of rapidly quenched precursor expands the range towards lower temperatures. GFA of the alloys was estimated by several melt quench techniques (casting, spinning and INROWASP). Fully amorphous samples with the thickness of 0.06–0.5 mm were prepared.

We report a nuclear magnetic resonance (NMR) study of slow atomic motions in Zr-Ti-Cu- Ni-Be bulk metallic glasses. The employed 9Be spin alignment echo technique is able to probe Be motions with jump rate below 0.1 Hz. It was found that the Be motion is spatially homogeneous. The jump rate follows a perfect Arrhenius temperature dependence. The measured activation enthalpy of 1.2 eV is nearly identical to that obtained by Be diffusivity measurement using elastic backscattering (EBS); this indicates that energy barriers are the same for short and long range Be motions. The present work provides direct experimental evidences that exclude vacancy-assisted and interstitial diffusion mechanisms for Be motions in these systems. The result is interpreted in terms of the spread-out free volume fluctuation mechanism.

Nuclear magnetic resonance (NMR) was applied for structural investigations of the bulk metallic glass system Zr55Cu30A110Ni5. The 63Cu as well as 27Al resonance was used. For both nuclei, two different spin-lattice relaxation rates were found which can be explained by different local environments of the nuclei.

A fast x-ray measurement system adopting the geometry of the Debye-Scherrer camera in combination with an imaging plate has been developed for the structural study of supercooled liquid. We carried out the anomalous x-ray scattering (AXS) measurement as well as the ordinary x-ray diffraction measurement with this system in Zr60Al15Ni25 supercooled liquid at 720K above the glass transition temperature (693K). A whole diffraction profile of very good counting statistics that even fits to the AXS analyses is obtained for a very short time (≅600s). The analyses of scattering data observed in the Zr60Al15Ni25 supercooled liquid for various annealing times in this system provide us information on a change of local atomic structures in the liquid state.

Glassy Zr65Al10Ni10Cu15 wires were produced in the diameter range up to about 310 µm by a melt extraction method using a copper wheel in an argon atomospher The grass transition temperature (Tg) and crystallization temperature (Tx) are 652K and 757K, respectively, and the temperature interval of the supercooled liquid, ΔTx(=Tx-Tg) is 105K, in agreement with those for the corresponding melt-spun ribbon. The wires have a nearly real circular cross section and good mechanical properties.

Bulk metallic glasses in the form of amorphous coatings were produced by detonation gun spraying of eutectic alloy containing iron, chromium, phosphorus and carbon. The thickness of the resulting homogeneous amorphous deposit may be up to 2–3 millimeters. The heat capacity, the coefficient of thermal expansion, the corrosion resistance, the hardness and the short range order structure parameters were studied for the bulk metallic glasses and thin ribbon. The investigation revealed that time (for 3 year) and temperature (300–670K) related structural relaxation in amorphous alloys is a nonmonotonic wavelike process having an irreversible nature. The amorphous detonation sprayed coatings have been successfully employed for improving service properties of medical instruments.

The bulk amorphous alloy (Mg1-xAlx)60Cu30Y10 has been studied, in particular the influence of Al concentration on the glass forming ability and on the various transition temperatures. The amorphous single phase has been obtained for x up to 0.07 by casting into a wedge-shaped copper mold. The amorphous alloys were investigated by differential scannning calorimetry (DSC). All the specimens with x = 0 - 0.07 show a clear glass transition. The crystallization temperature decreases with increasing Al concentration, while the temperatures of the glass transition, melting and solidification change only slightly. The DSC measurements show that for Al contents below 0.05 the first exothermic peak which corresponds to crystallization, consists of two overlapping peaks. To clarify the origin of the splitting of the first exothermic peak, the crystallization process of Mg60Cu30Y10 alloy has also been studied by x-ray diffraction.

Crystallization mechanism and kinetics of a Pd40Cu30Ni10P20 glass was investigated in a wide temperature range from 603 (near the glass transition temperature) to 764 K (near the equilibrium melting temperature) by using an isothermal annealing treatment for nucleation and growth. The nucleus density (nv) is about 5 × 1013 nuclei/m3 and is independent of annealing temperature. Therefore, it is assumed that the crystallization of the alloy was dominated by heterogeneous nucleation due to “quenched-in nuclei”. On the other hand, the crystal growth rate (Uc) increases from 1.07 × 10− to 5.68 × 10−5 m/s with rising annealing temperature from 603 to 764 K. These values of Uc are 2–3 orders of magnitude larger than the calculated Uc on the basis of Classical Nucleation and Growth Theory (CNT). Furthermore, the glass-forming ability of the alloy will be discussed in the framework of the present results.

Preliminary phase equilibrium relationships have been established in the Zr-Cu-Al system at 800 °C, using a combination of X-ray diffraction and electron probe microanalysis. These results are similar to previous investigations that have been reported in the literature. Several ternary phases are found to exist in this system, many of which lie within the gross compositional vicinity of interest to bulk amorphous alloy formation. The equilibrium phases present in the alloy Zr65Cu27.5A17.5, which exhibits a particularly high Tx-Tg in the amorphous state, are Zr2Cu and minor amounts of two additional phases: Zr3Al and what may be a ternary phase with a composition near Zr6CuAl3. When the 800 °C phase diagram isotherm is correlated with the known glass forming composition range of the Zr-Cu-Al system, it is found that the best glass forming behavior is confined to those regions of the diagram in which all equilibria include Zr-Cu constituent binary phases and Al-poor ternary phases. This may suggest that difficulties in the nucleation of these binary phases plays a role in the glass forming ability of Zr-Cu-Al and related higher order alloys.