The pair density function analysis of neutron diffraction data of Fe-based metallic glasses of the Zr and Mo series shows how the local atomic structure changes by chemical substitution. The results provide evidence for short-range chemical reorganization accompanied by a volume contraction that could in turn be associated with stronger glass forming ability. While the existence of chemical short-range topological ordering is enhanced in both systems by alloying with a transition metal such as Mn, locally, the atomic structure changes in a way that corresponds to an increase in bonding interactions. The shortening of bonds is also related to volume contraction that can in turn be associated with a reduction of the ferromagnetic coupling of the Fe sublattice and to a lower Curie transition temperature.

The effect of the supercooled liquid region on the primary crystallization of Al85Ni7Gd8 metallic glass, which exhibits a clear glass transition before its primary crystallization, was evaluated systematically under different annealing conditions, including isothermal annealing at different temperatures and non-isothermal annealing employing different heating rates. It was found that isothermal annealing within the supercooled liquid region and non-isothermal annealing at small heating rates (≤ 5 °C/min) result in the co-precipitation of fcc-Al and Al compound(s). When isothermal annealing is done at temperatures where partial crystallization is involved, or non-isothermal annealing is carried out at a larger heating rate, the primary crystallization product is a single phase of fcc-Al. The effect of the supercooled liquid region on the crystallization product is discussed in detail.

Ternary and quaternary bulk amorphous Pd-Ni-P and Pd-Ni-Fe-P alloys were prepared by fast quenching in water. X-ray photoemission spectra of Pd-Ni-P have previously been measured by Alamgir et al. (Phil. Mag. B 79, 239 (1999)). These results have been extended by (a) measuring the Auger spectra and the Auger parameters of key elements, (b) cross correlating the data with PdNi binaries, and (c) investigating the effects of adding Fe. It is shown that the Auger parameters change systematically across the composition range and the results are discussed in terms of possible charge transfer, changes in d-band character, and covalent bonding.

Recently, a self-consistent dynamic free volume model was proposed to analyze the Newtonian and non-Newtonian uniform steady-state flow data for bulk glass forming liquids such as those of the Zr-Ti-Cu-Ni-Be Vitreloy family. The model is based on the traditional free volume model of the glass transition, the Vogel-Fulcher-Tammann (VFT) equation, and a simple treatment of free volume production and annihilation during flow. It was shown that the model results in a simple one-parameter fit to extend the VFT equation for Newtonian flow to non-Newtonian uniform steady-state flow. We further extend the model to include transient uniform flow, by considering the evolution of free volume with time.

Due to their unique mechanical properties, bulk metallic glasses (BMG) have potential for biomedical applications. Biocompatibility and corrosion tests of a zirconium-based BMG showed comparable behavior to current implant alloys. Mechanical properties, such as an elastic limit of 2% and a yield strength of 1700 MPa, are significantly higher than current implant alloys. In addition, it was found that medical MRI images of BMG, possibly due to the amorphous structure, are significantly better than other alloys even though the reference alloy contains 14.6 at.% Ni. Nickel-free compositions also retained similar glass forming characteristics and showed even better MRI images. Edge holding for cutting tool applications was demonstrated. Fatigue tests were performed in simulated body conditions and directly compared to Ti-6 Al-4 V. While one specimen failed at more than 3,000,000 cycles at 500 MPa, there was much scatter in the data. Further concentration on processing issues to produce pore free material is needed to produce reliable materialfor prototype development. Potential uses, especially associated with an interventional MRI for MRI guided surgeries, will be discussed.

We report on mechanical alloying of elemental powders with nominal composition Zr55Cu30Al10Ni5 together with up to 30 vol.% of ZrC particles which results in the formation of a metallic glass matrix in which the carbide particles are homogeneously dispersed and, at the same time, reduced to nanometer size. The thermal stability is investigated by isochronal differential scanning calorimetry and is found to be strongly affected by increasing the ZrC volume fraction. Comparison with calorimetric data for single-phase mechanically alloyed Zr-Cu-Al-Ni-C glassy powders suggests that dissolved carbon, originating from non-negligible ZrC-dissolution processes during mechanical alloying, is responsible for the changes in the glass transition and the crystallization behavior. Isothermal calorimetric data are also presented and discussed in the framework of the Johnson-Mehl-Avrami model. The carbon atoms dissolved in the glassy phase are suggested to slow down the kinetics of overall crystallization. On the other hand, for large ZrC volume fractions nucleation of crystalline phases is promoted by the second-phase particles and changes in the Avrami exponent from n = 4 to n = 3 suggest that the nucleation rate approaches zero after the early stages of crystallization.

Bulk metallic glasses (BMG) exhibit high strength but limited ductility due to their inhomogeneous deformation behavior under load, which seriously limits their application. To prevent the inhomogeneous deformation, attempts have been made by introducing in situ formed ductile dendritic phases in present study. Ti-base BMG-forming alloys were selected and modified by adding refractory metals Nb, Ta, Mo and Zr. Ductile dendrites / nanostructured matrix composites were synthesized which exhibit a plastic strain larger than 14% together with high strength (ultimate strength higher than 2400 MPa). The experimental results show evidence that shear banding is the main deformation mode in nanostructured matrix. The localized shear bands are limited in the inter-dendrite regions by micrometer-sized dendrites. The dendrites act as obstacles to limit the excessive deformation in the localized shear bands and contribute to the plasticity by dislocations.

Ti255Hf50Ni25 metallic glasses, prepared by rapid quenching, are strongly metastable with a 65°C separation between the glass transition temperature, Tg = 335°C, and the onset temperature for primary crystallization. The deep metastability of the glass is likely due to sluggish nucleation and growth kinetics, limited by the Hf diffusion. The glass crystallizes to a nano-scale microstructure consisting of an icosahedrally symmetric ordered phase. This phase is metastable and transforms to a stable Ti2Ni-type phase with annealing at higher temperatures. The primary crystallization to a metastable icosahedrally-ordered phase suggests that the local structure of the glass contains a high degree of icosahedral short-range order. Here, glass formation and crystallization were studied in alloys containing 2 at.% of Si and P.

Various compositions of P2O5-TeO2-ZnO glasses were prepared by using a combinatorial glass preparation system including a batch-preparing apparatus and a multi-sample casting machine, and the compositional dependence of glass forming tendency and thermal properties were intensively investigated. The samples exhibited a variety of colors, such as transparent, yellow, wine red and brown depending on its composition. Analyses with scanning electron microscopy and X-ray photoelectron spectroscopy revealed that the reddish coloration is responsible for colloidal suspension of nanometer sized elemental Te particles.

A new method is developed to directly exhibit glass transition in Zr-Ti-Cu-Ni-Be bulk glass-forming alloy under high pressure in metallic glass. Via the method, we derive an increase of glass transition temperature, Tg with pressure of 5.6 K/GPa, and a formation volume (ΔVf) of 6.5 Å3 for diffusion and the migration volume (ΔVm) of 6.5 Å3. The glass transition under high pressure is simulated based on the free-volume theory, and the simulations are consistent with the experimental observations.

Melt-quenched AsxGexSe1–2x glasses over the composition range, 0 < x < 0.26, are examined in Raman scattering, T-modulated Differential Scanning Calorimetry (MDSC), and 119Sn Mossbauer spectroscopy measurements. The non-reversing enthalpy near Tg, ΔHnr(x), accessed from MDSC shows a global minimum (∼ 0) in the xc(1) = 0.09 < x < xc(2) = 0.16 range, and increases by an order of magnitude both at x < xc(1) and at x > xc(2). Raman mode frequency of corner-sharing Ge(Se1/2)4 tetrahedra studied as a function of x, also shows three distinct regimes (or power-laws, p) that coincide with ΔHnr(x) trends. These regimes are identified with mechanically floppy (x < xc(1)), intermediate (xc(1) < x < xc(2)), and stressed-rigid (x > xc(2)) phases. The Raman elasticity power-law in the intermediate phase, p1 = 1.04(3), and in the stressed rigid phase, p2= 1.52(5), suggest effective dimensionalities of d = 2 and 3 respectively.

Molecular Dynamics simulation was carried out to study the glass transition and crystallization in the metal-metalloid binary system with pair-wise potentials. The results show that a repulsive potential between metalloid (small) atoms increases the glass forming ability. The observation is consistent with the recent theory of bulk metallic glass formation through local glass transition and nano-glass formation. The theory predicted that the compositional short-range order (CSRO) prevents the small atom pairing so as to increase the glass forming ability (GFA). The present results demonstrate the important role of CSRO in bulk metallic glass formation.

The recent development of multi-component alloys with exceptional glass forming ability has allowed the processing of large amorphous metal samples. The possibility of formation of thermal tempering stresses during the processing of these bulk metallic glass (BMG) specimens was investigated using the (1) instant freezing, and (2) viscoelastic models. Both models yielded similar results although from vastly different approaches. It was shown that fast convective cooling of Zr41.2Ti13.8Cu12.5Ni10Be22.5 plates could generate significant compressive stresses on the surfaces balanced with mid-plane tension. The crack compliance method was then employed to measure the stress profiles in a BMG plate that was cast in a copper mold. These profiles were roughly parabolic suggesting that thermal tempering was indeed the dominant residual stress generation mechanism. However, the magnitude of the measured stresses (with peak values of only about 1.5% of the yield strength) was significantly lower than the modeling predictions. Possible reasons for this discrepancy are described in relation to the actual casting process and material properties.

The high temperature deformation of the Zr41.2Ti12.5Cu13.8Ni10Be22.5 bulk metallic glass (BMG) is studied in the supercooled liquid region. Both fully amorphous and partially crystallized states are investigated. In the studied experimental domain, the amorphous alloy exhibits a Newtonian behavior at high temperature and/or low strain rate whereas a transition to non-Newtonian behavior is observed when the temperature is decreased and/or the strain rate is increased. In the Newtonian domain, the dependency of the viscosity upon temperature can be described by an Arrhénius law. As far as the as-received alloy is maintained at high temperature for which phase separation and primary crystallisation is expected, the flow stress continuously increases, which is at least partly attributed to a change in the residual amorphous phase.

The formation of the primary crystals appearing during isothermal annealing of the Zr46.8Ti8.2Cu7.5Ni10Be27.5 (Vit4) bulk metallic glasses has been studied by in-situ neutron diffraction, DSC, high resolution TEM and electron diffraction. We have evidenced that the primary phase appearing on the isothermal plateau at 620 K is quasicrystalline and is beryllium free. Moreover, we have prepared an alloy with the composition determined by EDX (without beryllium), and studied the formation of quasicrystals in this alloy. A comparison is done between the quasicrystalline phases appearing during the annealing of Vit4 and the quasicrystals prepared without beryllium in an amorphous alloy prepared by melt spinning. In particular they have the same intensities and peak positions in the diffraction studies.

The applicability of the confusion principle and size factor in glass formation has been explored by following different combinations of isoelectronic Ti, Zr and Hf metals. Four alloys of nominal composition Zr41.5Ti41.5Ni17, Zr41.5Hf41.5Ni17, Zr25Ti25Cu50 and Zr34Ti16Cu50 have been rapidly solidified to obtain an amorphous phase and their crystallisation behaviour has been studied. The Ti-Zr-Ni alloy crystallises in three steps. Initially this alloy precipitates icosahedral quasicrystalline phase, which on further heat treatment precipitates cF96 Zr2Ni phase. The Zr-Hf-Ni alloy can not be amorphised under the same experimental conditions. The amorphous Zr-Ti-Cu alloys at the initial stages of crystallisation phase-separateinto two amorphous phases and then on further heat treatment cF24 Cu5Zr and oC68 Cu10Zr7 phase are precipitated. The lower glass-forming abilityof Zr-Hf-Ni alloy and the crystallisation behaviour of the above alloys has been studied. The rationale behind nanoquasicrystallisation and the formation of other intermetallic phases has been explained.

The relationship between coercivity (Hc) and magnetostriction (λs) of the glassy Fe-(Al, Ga)-(P, C, B, Si) alloys has been discussed. The glassy Fe-(Al, Ga)-(P, C, B, Si) alloys exhibit lower Hc and lower Is compared with the conventional Fe-based amorphous alloys with the same λs and Fe content, respectively. Theoretical analysis on the basis of domain-wall movement suggests that the low Hc results from the long-range homogeneous structure of the glassy alloys, which realizes a low density of pinning centers. The good combination of high glass-forming ability and good soft magnetic properties (especially low Hc) indicates the possibility of future development as new bulk glassy soft magnetic materials.

We study a binary Lennard-Jones mixture below the glass transition with molecular dynamics (MD) simulations. To investigate the dynamics of the system we define single particle jumps via their single particle trajectories. We find two kinds of jumps: metastable jumps, where a particle jumps back and forth between two or more states, and real jumps, where a particle does not return to any of its former states. For both the real and metastable jumps we present as a function of temperature the number of jumps, jump size, time between jumps, and energy.

Alloy formation in nanometer-sized particles has been studied as a function of the particle size by in-situ transmission electron microscopy using particles in the Au-Sn and Sn-Bi systems. When the size of particles is larger than a critical value, essentially similar phase equilibrium was observed in nanometer-sized particles and bulk materials in the both systems. But a solid amorphous phase was formed over a compositional range near the eutectic composition when the size of particles was smaller than about 7 nm in diameter in the former system, whereas a fluid amorphous phase was formed when the size of particles is smaller than about 10 nm in diameter in the latter system. These amorphous phases directly changed into liquid phases upon heating and solidified into amorphous phases upon subsequent cooling. The formation of these thermodynamically stable amorphous phases can be attributed to the the suppression of the eutectic temperature (Teu) associated with size reduction being so large that Teu is below the glass transition temperature (Tg).

The transformation from Newtonian to non-Newtonian viscous flow at the glass transition of Pd- and Zr-based alloy glasses has been investigated in compressive tests under either a constant strain rate, or a constant load. The transition occurs at a critical stress being nearly independent of temperature. The mechanism of the transition thus has been attributed to the stress-induced structural relaxation. This paper describes the evidence of stress-induced disorder as indicated by the change in the viscosity with stress and the evolution of specific heat of the alloy glasses subjected to non-Newtonian steady-state viscous flow. Also presented in this paper is the in-situ observation of structural disorder, by direct measurements of the temperature change of sample, in particular the soften process during a constant load deformation. The heat of evolution is then calculated, and found to scale as the logarithm of the normalized viscosity during entire deformation. This result implies that the relationship between the structural disorder, as indicated by the enthalpy change and viscosity is the same in the transient state during deformation as well as in the steady-state flow process. This is conceptionally very important in that it enables us to introduce a fictive stress which indirectly represents the glass structure.