The glass transition is the most enduring grand-challenge problem in contemporary condensed matter physics. Here, we review the contribution of colloid experiments to our understanding of this ...problem. First, we briefly outline the success of colloidal systems in yielding microscopic insights into a wide range of condensed matter phenomena. In the context of the glass transition, we demonstrate their utility in revealing the nature of spatial and temporal dynamical heterogeneity. We then discuss the evidence from colloid experiments in favor of various theories of glass formation that has accumulated over the last two decades. In the next section, we expound on the recent paradigm shift in colloid experiments from an exploratory approach to a critical one aimed at distinguishing between predictions of competing frameworks. We demonstrate how this critical approach is aided by the discovery of novel dynamical crossovers within the range accessible to colloid experiments. We also highlight the impact of alternate routes to glass formation such as random pinning, trajectory space phase transitions and replica coupling on current and future research on the glass transition. We conclude our review by listing some key open challenges in glass physics such as the comparison of growing static length scales and the preparation of ultrastable glasses that can be addressed using colloid experiments.
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Bulk metallic glass (BMG) provides plentiful precise knowledge of fundamental parameters of elastic moduli, which offer a benchmark reference point for understanding and applications of the glassy ...materials. This paper comprehensively reviews the current state of the art of the study of elastic properties, the establishments of correlations between elastic moduli and properties/features, and the elastic models and elastic perspectives of metallic glasses. The goal is to show the key roles of elastic moduli in study, formation, and understanding of metallic glasses, and to present a comprehensive elastic perspectives on the major fundamental issues from processing to structure to properties in the rapidly moving field. A plentiful of data and results involving in acoustic velocities, elastic constants and their response to aging, relaxation, applied press, pressure and temperature of the metallic glasses have been compiled. The thermodynamic and kinetic parameters, stability, mechanical and physical properties of various available metallic glasses especially BMGs have also been collected. A survey based on the plentiful experimental data reveals that the linear elastic constants have striking systematic correlations with the microstructural features, glass transition temperature, melting temperature, relaxation behavior, boson peak, strength, hardness, plastic yielding of the glass, and even rheological properties of the glass forming liquids. The elastic constants of BMGs also show a correlation with a weighted average of the elastic constants of the constituent elements. We show that the elastic moduli correlations can assist in selecting alloying components with suitable elastic moduli for controlling the elastic properties and glass-forming ability of the metallic glasses, and thus the results would enable the design, control and tuning of the formation and properties of metallic glasses. We demonstrate that the glass transition, the primary and secondary relaxations, plastic deformation and yield can be attributed to the free volume increase induced flow, and the flow can be modeled as the activated hopping between the inherent states in the potential energy landscape. We then propose an extended elastic model to understand flow in metallic glass and glass-forming supercooled liquid, and the model presents a simple and quantitative mathematic expression for flow activation energy of various glasses. The elastic perspectives, which consider all metallic glasses exhibit universal behavior based on a small number of readily measurable parameters of elastic moduli, are presented for understanding the nature and diverse properties of the metallic glasses.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
The effects of C/B ratio on the glass-forming ability (GFA) and low-temperature magnetic properties of Fe42Co6Cr15Mo14CxB21−xTm2 (x = 9, 11, 13, 15 and 17 at%) metallic glasses are studied in this ...work. The critical diameter of the bulk metallic glasses changes from 2 mm to 12 mm when x increases from 9 to 15, due to the dense atomic packing and strong liquid behavior. An Fe42Co6Cr15Mo14C15B6Tm2 amorphous master ingot with a diameter of 16.5 mm is produced via arc melting and furnace cooling. With increasing C/B ratio, the antiferromagnetic interactions between Fe and Cr is decreased, leading to the increasing Curie temperature and activation energy of spin-glass behavior. A stable magnetocaloric transition at a large temperature range is achieved in Fe42Co6Cr15Mo14C15B6Tm2 glassy ribbon. The fracture strength of the as-cast bulk metallic glasses increases firstly and then decreases with increasing C/B ratio, reaching the highest fracture strength of 4594 MPa when x = 15.
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•Effect of C/B ratio on GFA and magnetic behavior of Fe-based BMGs are studied.•An amorphous master ingot with a diameter of 16.5 mm is fabricated.•Activation energy of spin-glass behavior rises with increasing C/B ratio.•A stable magnetocaloric transition at a large temperature range is achieved.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Bulk metallic glass (BMG) samples are amalgamated by high-energy ball milling using the general formula (Ni75Cr15Si10)100−xTix (labelled as NCSTx, where x = 0,4, 8 and 12 at.%). The crystallinity and ...phase attribution properties of nickel (Ni), chromium (Cr), silicon (Si) and titanium (Ti) are scrutinized using the XRD analysis. The trend related to glass-forming ability (ΔT) and the GFA parameter (γ) is NCST8 > NCST12 > NCST4 > NCST0, which confirms that NCST8 sample shows superior glass-forming ability. The reduced glass transition temperature (Trg) for all the present BMG systems is greater than 0.5, which offers its good thermal stability and glass-forming ability (GFA). Corrosion studies suggested that a sample, having dynamic nature towards corrosion resistance and potential (Ec) (NCST8, (Ni75Cr15Si10)92Ti8), exhibits relatively lower values of both ic (4.7 × 10−4 A/cm2) and ip (0.0079 A/cm2), as recommended in potentio-dynamic findings.
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BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The present work is focused on the production of gas-atomized powders of the (Fe0.6Co0.4)0.75B0.2Si0.0596Nb4 (at%) glass-forming alloy and their consolidation within the supercooled liquid interval ...by hot extrusion. The thermal history of the powders during gas atomization was modeled using momentum and energy conservation equations. While these calculations predicted that the atomized droplets were subjected to solidification rates over 103 K/s, some crystalline phases were still experimentally observed in the atomized powders. The crystalline structure of these phases was determined using synchrotron x-ray diffraction experiments. The atomized powders with diameters between 53 and 75 µm were encapsulated in copper cans and hot extruded at 565 °C using an extrusion ratio of 3:1. The extrusion produced deformed powders, suggesting that the process was successfully conducted between the glass transition and crystallization temperatures. Minimal crystallization occurred during consolidation, as quantified by optical microscopy and differential scanning calorimetry techniques. Nanocrystals of about 10 nm, dispersed in a glassy matrix, were observed in the extruded powders. Furthermore, a discontinuous layer of α-(Fe, Co) phase was present between the extruded particles. The presence of hard micro-size crystalline particles among the powders led to a highly heterogeneous flow during extrusion. Due to stress concentration at the interface between glassy and crystalline particles, cracks sometimes nucleated and grew along the boundaries between the extruded particles. The results shown in this work give an important contribution to the understanding of the effect of crystalline particles on the processing of metallic glass matrix composites within the supercooled liquid interval.
•Gas atomization of an Fe-based glass forming alloy.•Mathematical modelling of droplets thermal history during gas atomization process.•Hot-extrusion of Fe-based metallic glass powders within the supercooled liquid interval.•Influence of hard-crystalline particles on the flow behavior of metallic glass powders during hot extrusion.•Characterization of the interface between hot-extruded metallic glass powders.
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The influence of substituting strontium for calcium in the following glass series 49.46 SiO
2–1.07 P
2O
5–(23.08-X) CaO–X SrO–26.38 Na
2O was studied on the physical properties. Solid state nuclear ...magnetic resonance and vibrational spectroscopy showed that the glasses were predominantly composed of Q
2 silicate chains. Addition of strontium did not result in any structural alteration of the glass network due to the similar role of SrO compared with that of CaO. The density increased with strontium content whilst the oxygen density decreased indicating a more expanded glass network. The glass transition temperature reduced with strontium substitution in a linear fashion and there was no evidence of a mixed alkaline earth effect with a lower than expected glass transition temperature. Dilatometric softening points also reduced with increasing strontium content, whilst the thermal expansion coefficients increased. The results are consistent with a weaker network as a result of the lower charge to size ratio of Sr
2+ compared to Ca
2+.
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The serrated flow behavior of Zr.sub.61.7Al.sub.8Ni.sub.13Cu.sub.17Sn.sub.0.3 bulk metallic glass with different aspect ratios was investigated. For the samples with aspect ratios below 2.0, the ...serrated flow behavior changes from uniform to nonuniform with increasing aspect ratios. The histograms of normalized stress drop magnitude all exhibit a peak shape and the mean stress drop magnitude increases with increasing aspect ratios. The serrated flow behavior is special and can be divided into two stages for the sample with aspect ratio of 2.5. At the first stage, the serrations exhibit a nonuniform behavior and the histogram of normalized stress drop magnitude exhibit a peak shape. At the second stage, the serration size increases significantly and the histogram of normalized stress drop magnitude exhibits a sporadic behavior. The reason for the appearance of the complex serrated flow behavior may probably be attributed to the complex interaction of multiple shear bands formed during the deformation.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this work, the effects of Ag substitution for Ti in Zr56Cu24Al9Ni7Ti4-xAgx (x = 0, 1, 2, 3, and 4 at%) bulk metallic glasses (BMGs) on the glass-forming ability, thermal stability and mechanical ...properties are investigated. The present research shows that the critical diameter increases to 6–8 mm for Ag content of x = 2 and 3 at%. Additionally, with increasing in the content of Ag, with a rod diameter of 3 mm, the glass-forming ability and thermal stability were effectively improved. The largest ultimate fracture strength and plastic strain were observed for alloys where x = 2 with a rod diameter in 3 mm (1863 (± 25) MPa and 7.9 (±0.6) %, respectively). Different fracture modes were observed using scan electron microscopy after compressive testing. This work illustrates that Ag can play an important role in improving glass-forming ability, thermal stability and mechanical properties for amorphous alloys.
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IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SBCE, SBJE, UILJ, UPUK
The structure of metallic glasses (MGs) has been a long-standing mystery. On the one hand, MGs are amorphous materials with no long-range structural order; on the other hand, topological and chemical ...short-to-medium range order is expected to be pronounced in these alloys, due to their high atomic packing density and the varying chemical affinity between the constituent elements. The unique internal structure of MGs underlies their interesting properties, which render MGs potentially useful for various applications. While more and more glass-forming alloys have been developed in recent years, fundamental knowledge on the structural aspect of MGs remains seriously lacking. For example, how atoms pack on the short-to-medium range, how the structure differs in different MGs and changes with composition, temperature, and processing history, and more importantly, how the structure influences the properties of MGs, are still unresolved questions. In this paper, we review the tremendous efforts over the past 50years devoted to unraveling the atomic-level structure of MGs and the structural origin of their unique behaviors. Emphasis will be placed on the progress made in recent years, including advances in structural characterization and analysis of prototypical MGs, general structural models and fundamental principles, and the correlations of thermodynamic, kinetic, and mechanical properties with the MG structures. Some widely observed property-property correlations in MGs are also examined from the structural perspective. The insights summarized are shown to shed light on many intriguing behaviors of the MG-forming alloys and expected to impact the development of MGs. Outstanding questions in this important research area will also be outlined.
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