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The amorphous/amorphous nanolaminates (A/ANLs) have aroused great attentions owing to their tunable structure and enhanced mechanical properties. However, the plastic deformation mechanism of A/ANLs have yet been clarified. Here, we systematically examined the mechanical properties and deformation behavior of series of NiNb/ZrCuNiAl A/ANLs via nanoindentaion test. It was found that both the amount and morphology of amorphous/amorphous interface (A/AIs) played crucial roles in the plastic deformation of A/ANLs. Less and straighter A/AIs facilitated multiple shear banding deformation, of which the hardness increased with decreasing layer thickness, as the A/AIs hindered the propagation of shear bands (SBs). Whilst, more and wavier A/AIs promoted homogeneous deformation, of which the hardness stayed at a much lower value and was relatively irrelevant with the layer thickness, for the promoted activation of shear transformation zones by A/AIs. Our results provide guidance for modifying the mechanical properties of amorphous alloys with interface engineering design.

Lunar glasses with different origins act as snapshots of their formation processes, providing a rich archive of the Moon's formation and evolution. Here, we reveal diverse glasses from Chang’E-5 (CE-5) lunar regolith, and clarify their physical origins of liquid quenching, vapor deposition and irradiation damage respectively. The series of quenched glasses including rotation-featured particles, vesicular agglutinates and adhered melts, record multiple-scale impact events. The abundant micro impact products, like micron to nano-scale glass droplets or craters, highlight that the regolith is heavily reworked by frequent micrometeorite bombardment. Distinct from Apollo samples, the indigenous ultra-elongated glass fibers drawn from viscous melts and the widespread ultra-thin deposited amorphous rims without nanophase iron particles both indicate a relatively gentle impact environment at the CE-5 landing site. The clarification of multitype CE-5 glasses also provides a catalogue of diverse lunar glasses, making more Moon's mysteries recorded by glasses capable to be deciphered in future.

Ir-Ni-Ta metallic glasses (MGs) exhibit an array of superior high-temperature properties, making them attractive for applications at high temperatures or in harsh environments. However, Ir-Ni-Ta bulk MGs are quite brittle and often fracture catastrophically even before plastic yielding, significantly undercutting their high-strength advantage. Here, we show that the Ir-Ni-Ta MGs are not intrinsically brittle, but rather malleable when the feature size is reduced to micro/nano-scales. All tested Ir-Ni-Ta MG micropillars with a diameter ranging from ~500 nm to ~5 µm display a large plastic strain above 25% (the maximum up to 35%), together with a yield strength up to 7 GPa, well exceeding the strength recorded in most metallic materials. The intrinsic shear stability of Ir-Ni-Ta MGs, as characterized by the normalized shear displacement during a shear event, is much larger than those malleable Zr- and Cu-based MGs. Our results suggest that Ir-Ni-Ta MGs are excellent candidates for micro/nanoscale structural applications used at high-temperature or extreme conditions.

Determination and conceptualization of atomic structures of metallic glasses or amorphous alloys remain a grand challenge. Structural models proposed for bulk metallic glasses are still controversial owing to experimental difficulties in directly imaging the atom positions in three-dimensional structures. With the advanced atomic-resolution imaging, here we directly observed the atomic arrangements in atomically thin metallic glassy membranes obtained by vapor deposition. The atomic packing in the amorphous membrane is shown to have a fractal characteristic, with the fractal dimension depending on the atomic density. Locally, the atomic configuration for the metallic glass membrane is composed of many types of polygons with the bonding angles concentrated on 45°–55°. The fractal atomic structure is consistent with the analysis by the percolation theory, and may account for the enhanced relaxation dynamics and the easiness of glass transition as reported for the thin metallic glassy films or glassy surface.

High saturation magnetic flux density (B

The correlation betweent deformation behavior and atomic-scale heterogeneity of bulk metallic glasses (BMGs) is critical to understand the BMGs’ deformation mechanism. In this work, three typical [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4, Fe39Ni39B14.2Si2.75P2.75Nb2.3, and Fe50Ni30P13C7 BMGs exhibiting different plasticity were selected, and the correlation between deformation behavior and atomic-scale heterogeneity of Fe-based BMGs was studied. It is found that the serrated flow dynamics of Fe-based BMGs transform from chaotic state to self-organized critical state with increasing plasticity. This transformation is attributed to the increasing atomic-scale heterogeneity caused by the increasing free volume and short-to-medium range order, which facilitates a higher frequency of interaction and multiplication of shear bands, thereby results in a brittle to ductile transition in Fe-based BMGs. This work provides new evidence on heterogeneity in plastic Fe-based BMGs from the aspects of atomic-scale structure, and provides new insight into the plastic deformation of Fe-based BMGs.

Developing materials with excellent properties has been the untiring pursuit of mankind. Metallic glasses (MGs) would be the ideal metallic materials if their size could be scaled up to be comparable to traditional metals. To address this challenge, a variety of approaches have been attempted over the past decades, including thermodynamics-based alloy, 3D printing and the recent artificial intelligence-guided optimal alloy. In this study, a facile and flexible route was demonstrated to manufacture giant MGs (GMGs) with diameters more than 100 mm through the thermo-joining process. The jointed GMG samples feature almost the same performance as the as-cast ones. The ability of manufacturing complex 3D components such as the Chinese Zodiacs was also demonstrated. Our approach might overcome the longstanding problem of glass forming ability (GFA) limitations in alloy systems and pave new concept and route to fabricate size unlimited MGs.

The multiscale structures in a Pd82Si18 binary bulk metallic glass before and after deformation were studied using electron microscopies, high-energy synchrotron X-ray diffraction, and small-angle scattering techniques. The experimental results revealed an enhancement of hierarchical structure heterogeneities on multiple length scales after deformation. Hierarchical multiple shear bands of high number density were observed after bending, introducing complex but periodically distributed residual strain. Pair distribution function analysis revealed that the connectivity of the short-range clusters on the medium-range scale determines the packing density difference between the tension side and the compression side in the sample after bending. In-situ synchrotron X-ray diffraction study also revealed a transformation of connection modes among short-range clusters under uniaxial tension and compression, which is consistent with those of triaxial tension/compression parts upon bending in Pd82Si18 glassy alloys. The nanoscale heterogeneities for metallic glasses after deformation observed by small-angle scattering and transmission electron microscopy may be attributed to the nanoscale amorphous phase separation and interacting multiple shear bands enhanced by plastic deformation. Our findings suggested that the enhancement of hierarchical heterogeneous structure on multiple length scales may explain the excellent plasticity of Pd-Si glassy alloys, deepening the understanding of structure-property relation during plastic deformation in metallic glasses.

Metallic glasses (MGs), with high density of low coordination sites and high Gibbs free energy state, are novel promising and competitive candidates in the family of electrochemical catalysts. However, it remains a grand challenge to modify the properties of MGs by control of the disordered atomic structure. Recently, nanostructured metallic glasses (NGs), consisting of amorphous nanometer-sized grains connected by amorphous interfaces, have been reported to exhibit tunable properties compared to the MGs with identical chemical composition. Here, it is demonstrated that electrodeposited Ni-P NG is characterized by an extremely high energy state due to its heterogeneous structure, which significantly promotes the catalytic performance. Moreover, the Ni-P NG with a heterogeneous structure is a perfect precursor for the fabrication of unique honey-like nanoporous structure, which displays superior catalytic performance in the urea oxidation reaction (UOR). Specifically, modified Ni-P NG requires a potential of mere 1.36 V at 10 mA cm

Strain glass is a glassy state with frozen ferroelastic/martensitic nanodomains in shape memory alloys, yet its nature remains unclear. Here, we report a glassy feature in strain glass that was thought to be only present in structural glasses. An abnormal hump is observed in strain glass around 10 K upon normalizing the specific heat by cubed temperature, similar to the boson peak in metallic glass. The simulation studies show that this boson-peak-like anomaly is caused by the phonon softening of the non-transforming matrix surrounding martensitic domains, which occurs in a transverse acoustic branch not associated with the martensitic transformation displacements. Therefore, this anomaly neither is a relic of van Hove singularity nor can be explained by other theories relying on structural disorder, while it verifies a recent theoretical model without any assumptions of disorder. This work might provide fresh insights in understanding the nature of glassy states and associated vibrational properties., Strain glass is a new glassy state characterized by frozen ferroelastic nanodomains. Here, the authors discover a low-temperature feature in the specific heat of a strain glass, which is similar to the well-known boson peak anomaly of structural glasses, but cannot be explained by existing mechanisms.

High strength and high ductility are often mutually exclusive properties for structural metallic materials. This is particularly important for aluminum (Al)-based alloys which are widely commercially employed. Here, we introduce a hierarchical nanostructured Al alloy with a structure of Al nanograins surrounded by nano-sized metallic glass (MG) shells. It achieves an ultrahigh yield strength of 1.2 GPa in tension (1.7 GPa in compression) along with 15% plasticity in tension (over 70% in compression). The nano-sized MG phase facilitates such ultrahigh strength by impeding dislocation gliding from one nanograin to another, while continuous generation-movement-annihilation of dislocations in the Al nanograins and the flow behavior of the nano-sized MG phase result in increased plasticity. This plastic deformation mechanism is also an efficient way to decrease grain size to sub-10 nm size for low melting temperature metals like Al, making this structural design one solution to the strength-plasticity trade-off., Strengthening a metallic alloy without sacrificing ductility remains challenging. Here, the authors develop a hierarchical nanostructured aluminium alloy composed of nanograins surrounding by metallic glass shells that has both ultrahigh strength and good ductility.

The surface-enhanced Raman spectroscopy (SERS) is a technique for the detection of analytes on the surface with an ultrahigh sensitivity down to the atomic-scale, yet the fabrication of SERS materials such as nanoparticles or arrays of coinage metals often involve multiple complex steps with the high cost and pollution, largely limiting the application of SERS. Here, we report a complex hierarchical metallic glassy (MG) nanostructure by simply replicating the surface microstructure of butterfly wings through vapor deposition technique. The MG nanostructure displays an excellent SERS effect and moreover, a superhydrophobicity and self-cleaning behavior. The SERS effect of the MG nanostructure is attributed to the intrinsic nanoscale structural heterogeneities on the MG surface, which provides a large number of hotspots for the localized electromagnetic field enhancement affirmed by the finite-difference time-domain (FDTD) simulation. Our works show that the MG could be a new potential SERS material with low cost and good durability, well extending the functional application of this kind of material.

Nanoscaled structure inhomogeneity has been identified to be an inherent characteristic of metallic glasses (MGs). Structural heterogeneities are also found to play a key role in designing and tuning the mechanical and relaxation behavior of MGs. As one peculiar member of the glassy family, U-based MGs show novel unique properties desirable for nuclear industries. However, the heterogeneous characteristics of this type of MGs have never been studied so far. In this study, U65Fe30Al5 and U60Fe27.5Al12.5 MGs were systematically investigated with nanoindentation of high sensitivity. They exhibit significantly different mechanical response for the primary and secondary creeps at varying loading rates and peak loads. Through analysis with the theoretical creep model for viscoelastic materials, U60Fe27.5Al12.5 MG is found to be in a more rigid state for the secondary (viscous) creep, suggesting more compact atomic structure for it. By further analysis and fitting with this model, dissimilar structural heterogeneity can be derived for these two MGs to account for their difference in creeping behavior. This work manifests that nanoindentation is a very useful technique to reveal heterogeneous structures of glassy alloys, and also to establish their composition-structure-property relationship.

A novel ductile Fe56Ni20Mo4P11C4B4Si1 bulk metallic glass (BMG) with saturation magnetic flux density of 0.93 T, coercivity of 1.9 A/m and plastic strain of 7% was successfully synthesized in this work. Effects of Ni and Si additions on mechanical properties and serrated flow behavior of Fe-Mo-P-C-B BMGs were systematically investigated. It was found that the simultaneous additions of Ni and Si are effective to improve the plasticity of Fe76Mo4P12C4B4 BMG as indicated by the increase in the plastic strain from 1.7% to 7%. Serrated flow behavior is not observed in Fe76Mo4P12C4B4 BMG. However, the chaos state occurs in Fe56Ni20Mo4P12C4B4 BMG, and eventually the self-organized critical (SOC) behavior appears in Fe56Ni20Mo4P11C4B4Si1 BMG. The stable shear-band dynamics leads to the formation of multiple shear bands, resulting in a complex deformation process follow the SOC dynamics. The improved plasticity might result from an increased number of potential shear transition zone sites, and a stronger tendency of forming shear band interactions. This work provides a perspective from serrated flow behavior to understand plastic deformation mechanism in Fe-based BMGs with different plasticity.

The improvement in strength is usually accompanied by ductility loss in structural materials, which is a long-standing conflict referred as the strength-ductility trade-off. Here we present a heterogeneous-structures-architecting strategy, in which we design bulk high-entropy alloys with the largely-enhanced strength-ductility trade-off, possessing a yield strength of 711 MPa, a tensile strength of 928 MPa, and a uniform elongation of 30.3%. Such an enhancement of the strength-ductility trade-off is due to the microstructure comprised with a combination of the non-recrystallized and recrystallized grains arranged in complex heterogeneous structures with a characteristic dimension spanning from the submicron scale to the coarse-sized scale. The heterogeneous structures in the high-entropy alloy are produced by cold-rolling, followed by intermediate-temperature-annealing. Our results demonstrate that heterogeneous designs can be accomplished effectively by simple thermal treatments, which offer a design strategy towards a new generation of high-strength and high-ductility high-entropy alloys.

Summary The surface of glass is crucial for understanding many fundamental processes in glassy solids. A common notion is that a glass surface is a thin layer with liquid-like atomic dynamics and a thickness of a few tens of nanometers. Here, we measured the shear modulus at the surface of both millimeter-size and micrometer-size metallic glasses (MGs) through high-sensitivity torsion techniques. We found a pronounced shear-modulus softening at the surface of MGs. Compared with the bulk, the maximum decrease in the surface shear modulus (G) for the micro-scale MGs reaches ~27%, which is close to the decrease in the G upon glass transition, yet it still behaves solid-like. Strikingly, the surface thickness estimated from the shear-modulus softening is at least 400 nm, which is approximately one order of magnitude larger than that revealed from the glass dynamics. The unusually thick surface is also confirmed by measurements using X-ray nano-computed tomography, and this may account for the brittle-to-ductile transition of the MGs with size reductions. The unique and unusual properties at the surface of the micrometer-size MGs are physically related to the negative pressure effect during the thermoplastic formation process, which can dramatically reduce the density of the proximate surface region in the supercooled liquid state., Graphical abstract, Public summary • The shear modulus and thickness of metallic glass (MG) surface is determined through torsion testing on micrometer-size wires • The surface region of MG wires has a significant shear-modulus softening close to the supercooled liquid, yet still behaves solid-like • The thickness of the soft surface of MG wires is at least 400 nm, which is about one order of magnitude larger than those revealed from surface dynamics • The unusually thick surface accounts for the brittle-to-ductile transition of the MGs with size reduction

Fracture of glasses can proceed through the organized nucleation, growth, and coalescence of nanocavities., Crack propagation is the major vehicle for material failure, but the mechanisms by which cracks propagate remain longstanding riddles, especially for glassy materials with a long-range disordered atomic structure. Recently, cavitation was proposed as an underlying mechanism governing the fracture of glasses, but experimental determination of the cavitation behavior of fracture is still lacking. Here, we present unambiguous experimental evidence to firmly establish the cavitation mechanism in the fracture of glasses. We show that crack propagation in various glasses is dominated by the self-organized nucleation, growth, and coalescence of nanocavities, eventually resulting in the nanopatterns on the fracture surfaces. The revealed cavitation-induced nanostructured fracture morphologies thus confirm the presence of nanoscale ductility in the fracture of nominally brittle glasses, which has been debated for decades. Our observations would aid a fundamental understanding of the failure of disordered systems and have implications for designing tougher glasses with excellent ductility.

We provide an intuitive interpretation for critical growth of an atomic-scale plastic flow unit in metallic glasses through energy conversion approach. An explicit expressions for the critical stress upon which the plastic flow unit can grow spontaneously is obtained. The growth of the atomic units is an competition process between the intrinsic configuration entropy change and the constraint effect of glassy matrix on the inelastic deformation of plastic flow unit. Our analysis shows that at the yielding point, the activation of a plastic flow unit should take the easiest path in the potential energy landscape. In this case, the change of intrinsic configuration entropy and the elastic constraint effect contribute equally to the activation energy barrier for the plastic flow unit. Our results provide quantificational insights on the microscopic origin of the plastic yielding of glassy solids.

The glass relaxation under ambient conditions is essential for understanding the nature of glass state, and has stimulated scientific and general public interests for centuries. However, owing to the extremely slow dynamics, experimental characterization of glass relaxation at ambient temperatures is quite challenging, and often takes several years. Here we report evident relaxation of metallic glasses at room temperature within the observation time of less one month when the feature size of glasses is reduced. The relaxation dynamics shows a size dependence similar to that on temperature, and an equivalence between size and temperature on affecting the relaxation dynamics is established. We also showed that a MG film with a feature size of ~ 10 nm at room temperature has a fast relaxation dynamics equivalent to that of a bulk MG near the glass transition temperature, indicating that the liquid-like behavior in glasses can be induced by size reduction.

Owing to the nonequilibrium nature, the energy state of metallic glasses (MGs) can vary a lot and has a critical influence on the physical properties. Exploring new methods to modulate the energy state of glasses and studying its relationship with properties have attracted great interests. Herein, we systematically investigate the energy state, mixing entropy and physical properties of Zr–Ti–Cu–Ni–Be multicomponent high entropy MGs by experiments and simulations. We find that the energy state increases along with the increase of mixing entropy. The yield strength and thermal stability of MGs are also enhanced by high mixing entropy. These results may open a new door on regulation of energy states and thus physical properties of MGs.

We report a novel plastic deformation mechanism of bulk metallic glass composites (BMGCs) containing metastable $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Ti}$ dendrites. Plastic deformation of the BMGCs beyond the ultimate tensile strength is mediated by cooperative shear events, which comprise a shear band in the glassy matrix and a continuous $\ensuremath{\omega}\text{\ensuremath{-}}\mathrm{Ti}$ band with a thickness of $\ensuremath{\sim}10\text{ }\text{ }\mathrm{nm}$ in the $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Ti}$ dendrite. The cooperative shear leads to serrated shear avalanches. The formation of narrow $\ensuremath{\omega}\text{\ensuremath{-}}\mathrm{Ti}$ bands is caused by high local strain rates during the cooperative shear. The cooperative shear mechanism enriches the deformation mechanisms of BMGCs and also deepens the understanding of $\ensuremath{\omega}\text{\ensuremath{-}}\mathrm{Ti}$ formation.

Metallic glasses response to the mechanical stress in a complex and inhomogeneous manner with plastic strain highly localized into nanoscale shear bands. Contrary to the well-defined deformation mechanism in crystalline solids, understanding the mechanical response mechanism and its intrinsic correlation with the macroscopical plasticity in metallic glasses remains long-standing issues. Through a combination of experimental and theoretical analysis, we showed that the shear banding process in metallic glasses exhibits complex chaotic dynamics, which manifests as the existence of a torus destroyed phase diagram, a positive Lyapunov exponent and a fractional Lyapunov dimension. We also demonstrated that the experimentally observed large plasticity fluctuation of metallic glasses tested at the same conditions can be interpreted from the chaotic shear-band dynamics, which could leads to an uncertainty on the appearance of the critical condition for runaway shear banding. Physically, the chaotic shear-band dynamics arises from the interplay between structural disordering and temperature rise within the shear band. By tuning the deformation parameters, the chaotic dynamics can be transformed to a periodic orbit state corresponding to a smaller plasticity fluctuation in metallic glasses. Our results suggest that the plastic flow of metallic glasses is a complex dynamic process, which is highly sensitive to initial conditions and reminiscent of the "butterfly effect" as observed in many complex dynamic systems.

A novel Fe39Ni39B12.82Si2.75Nb2.3P4.13 bulk metallic glass (BMG) with high notch toughness of 72.3 MPa m1/2, large plastic strain of 9.8%, high yield strength of 2930 MPa, and a large critical diameter of 2.5 mm was successfully developed. This BMG also exhibits excellent soft magnetic properties, i.e., higher saturation magnetic flux density of 0.86 T, extremely low coercivity of 0.65 A/m, and high effective permeability of 23,250 with high frequency stability. Its toughness value is the highest among Fe-based BMG family. The origin of high toughness was also investigated in detail by using synchrotron X-ray diffraction and aberration-corrected high-resolution transmission electron microscopy. It was found that the high toughness are attributed to atomic-scale structural heterogeneity that resulted from large free volume, high content of metal-metal bonds and high structural disorder degree, which can promote the multiple shear bands and hinder the subsequently propagation. This work provides useful guidelines for developing tough FeNi-based BMGs with high strength and excellent soft magnetic properties from an atomic structural perspective., Materials & Design, 191, ISSN:0264-1275, ISSN:1873-4197

NPG Asia Materials 12(1), 1-59 (2020). doi:10.1038/s41427-020-00241-4, The design of ductile heterogeneous metallic glasses (MGs) with enhanced deformability by purposely controlling theshear-band dynamics via modulation of the atomic-scale structures and local stress states remains a significantchallenge. Here, we correlate the changes in the local atomic structure when cooling to cryogenic temperature withthe observed improved shear stability. The enhanced atomic-level structural and elastic heterogeneities related to thenonaffine thermal contraction of the short-range order (SRO) and medium-range order (MRO) change thecharacteristics of the activation process of the shear transformation zones (STZs). The experimental observationscorroborated by Eshelby inclusion analysis and molecular dynamics simulations disclose the correlation between thestructuralfluctuations and the change in the stressfield around the STZ. The variations in the inclination axes of theSTZs alter their percolation mechanism, affect the shear-band dynamics and kinetics, and consequently delay shearfailure. These results expand the understanding of the correlation between the atomic-level structure and elementaryplastic events in monolithic MGs and thereby pave the way for the design of new ductile metallic alloys., Published by Macmillan Publishers Limited, part of Springer Nature, Tokyo

The multiscale structures in a Pd82Si18 binary bulk metallic glass before and after bending were studied using electron microscopy, high-energy synchrotron X-ray diffraction, and small-angle X-ray scattering. The experimental results revealed the enhancement of hierarchical structure heterogeneities on multiple length scales after deformation. Hierarchical multiple shear bands of high number density can be observed after bending, introducing complex but periodically distributed residual strain. Pair distribution function analysis revealed that the connectivity of the short-range cluster on the medium-range scale determines the packing density difference between the tension side and the compression side in the sample after bending. The electron density fluctuations on the nanoscale observed in the deformed part of the sample are indicative of a nanoscale amorphous phase separation induced by plastic deformation. Our findings will deepen the understanding of the plastic deformation mechanism of metallic glasses and shed light on designing glassy alloys of excellent plasticity and toughness through hierarchical multiscale structure heterogeneities.

Thin film metallic glasses (TFMGs) have attracted great attention due to their excellent functional properties and ease of fabrication as compared with bulk metallic glasses. Among them, TaW-based TFMGs have rarely been studied so far. Here, a novel Ta46.5W35Co18.5 TFMG was successfully developed using a magnetron co-sputtering system. The Ta46.5W35Co18.5 TFMG exhibits high hardness of 12.3 GPa, high elastic modulus of 159 GPa, pronounced plastic deformation behavior, and excellent corrosion resistance, i.e., low passive current density of 7.65 × 10−6 A/cm2 and high corrosion potential of 0.31 V, as well as good thermal stability with high onset crystallization temperature of 1100 K. In addition, the origin of these excellent properties was also investigated in detail by using X-ray diffraction and high-resolution transmission electron microscopy. It was found that, for the Ta46.5W35Co18.5 TFMG, its excellent corrosion resistance may be attributed to the amorphous structure, and the high hardness and good plastic deformation ability are caused by the unique atomic-scale structure with nanocrystals dispersed in the amorphous matrix. This work provides a useful guideline for developing TFMG system combined with excellent corrosion resistance, high hardness, and good thermal stability.

Bulk metallic glass composites (BMGCs) with in-situ formed crystals can display tensile ductility at room temperature, overcoming brittleness of monolithic bulk metallic glasses (BMGs). However, the ductility and toughness of BMGCs severely deteriorate at low temperatures, which has been a longstanding bottleneck hindering their low-temperature applications. Here, the low-temperature tensile properties of two Ti-based BMGCs containing stable β-Ti crystals with dislocation-mediated plasticity (Fe1) or shape memory β-Ti crystals (Fe0) were investigated. With temperature decreasing from 298 to 77 K, the strength of Fe1 increases but its tensile ductility decreases. In comparison, the shape memory Fe0 BMGC exhibits a simultaneous enhancement of strength and tensile ductility as temperature decreases from 298 to 143 K. The superior low-temperature properties of Fe0 are attributed to its combined structure of a glassy matrix and shape memory crystals. As temperature decreasing, the glassy matrix possesses an increased strength which softens as shear bands form, and the shape memory crystals are more inclined to deformation-induced martensitic transformation. Therefore, the combination of characteristic properties of metallic glasses and shape memory crystals in shape memory BMGCs can successfully overcome the low-temperature brittleness. These findings are believed to facilitate the development of BMGCs with superior low-temperature properties and promote their applications at low temperatures.

In the present work, we develop a series of binary Cu-Zr thin film metallic glasses (TFMGs) with tunable nanoscale structures by using direct-current (DC) magnetron sputtering technique. Depending on the chemical composition and the sputtering parameters, Cu-Zr TFMGs show variable nanoscale structures from nanocolumn to nanogranula. As compared to the metallic glassy ribbons with identical composition, the Cu-Zr TFMGs with nanoscale structures exhibit novel and unique thermal and mechanical properties. From nanoindentation study, it is found that the TFMGs with nanoscale structures display obvious reduced hardness (about 48–52%) and increased elastic modulus (about 7–23.8%) as compared to the metallic glassy ribbons. Moreover, the serrated flow behavior, as commonly observed from the load-displacement response in the nanoindentation of metallic glasses (MGs) is absence for nanostructured TFMGs, indicating the profound effects of nanoscale structural features on the plastic yielding and flow in TFMGs. This study provides a detail insight into a strategy of designing nanostructured TFMGs and obtaining tunable properties which is of great interest in the potential application of micro/nanoscale devices.

Plastic deformation of metallic glasses (MGs) has long been considered to be confined to nanoscale shear bands, but recently an affected zone around the shear band was found. Yet, due to technical limitations, the shear-band affected zone (SBAZ), which is critical for understanding shear banding and design of ductile MGs, has yet to be precisely identified. Here, by using magnetic domains as a probe with sufficiently high sensitivity and spatial resolution, we unveil the structure of SBAZs in detail. We demonstrate that shear banding is accompanied by a micrometer-scale SBAZ with a gradient in the strain field, and multiple shear bands interact through the superimposition of SBAZs. There also exists an ultra-long-range gradual elastic stress field extending hundreds of micrometers away from the shear band. Our findings provide a comprehensive picture on shear banding and are important for elucidating the micro-mechanisms of plastic deformation in glasses., Metallic glasses deform along nanoscale shear bands, and while it is known that they affect the neighboring glass regions, exactly how is unclear. Here, the authors use magnetic force microscopy to atomically resolve the shear-band affected zone and show its effects extends much further than previously thought.

The investigation on the stress relief of magnetic materials is important both for the industrial process and the academic research. In this work, the stress effects on the magnetic characteristics in Fe-based metallic glasses (MGs) are investigated under the applied bending stress and various annealing treatments. It was found that both the magnetic induction intensity B and effective permeability μ′ decrease while coercivity Hc increases with the applied compressive stress, indicating that the compressive effect is dominant on the magnetic characteristics in Fe78Si9B13 MG ribbons. We also found that the wide domain wall movement and the rotation of the narrow domains are seriously affected by internal stress during the magnetization process. Our results reveal that the stress relief plays a critical role in improving magnetic properties of Fe-based MGs and are helpful for understanding the correlations between the stress, microstructure change and magnetic softness in magnetic MGs.

Through detailed experimental and theoretical analyses, here we uncover the mechanism of plasticity initiation in the Ni-P nano-grained metallic glass (NGMG) which contains nano-sized hard amorphous inclusions and soft amorphous inter-granular regions. In this dual nano-phase amorphous structure, plasticity is mainly initiated through the elongation and coalescence of the amorphous nano-grains, resulting in a shear band much wider than in its monolithic counterpart. Consequently, the NGMG turns out to be softer at the microscopic scale. At the fundamental level, our finding provides a universal mechanism which explains the unusual strength weakening observed in a variety of dual nano-phase amorphous systems.

The excellent mechanical properties of recently developed polysynthetic TiAl-Ti3Al intermetallic single crystals lead to a high motivation to explore the micro-mechanical properties of their constitutional phases. However, the mechanical properties of the individual phases at the nanoscale are hard to obtain since the measurement requires a high lateral resolution and superior mechanical sensitivity. Here, using a method of scanning nanoindenter together with nanoDMA, we report the critical data of modulus maps and the nanoindentation hardness of their individual phases at the nanoscale. Furthermore, the yield strength and plasticity of the individual phases were obtained using an in situ nanoindentation on the focused ion beam machined nanopillars. The value of elastic modulus is measured to be about 140 and 180 GPa, respectively for α2-Ti3Al and γ-TiAl intermetallic phases, for samples with 0° lamellar orientation, which is higher than the value of about 120 and 160 GPa for the same phases in samples with 45° lamellar orientation. The relationship between the microscale and macroscale modulus can be described using the Voigt-Reuss approximation. More importantly, AFM results show that the plastic deformation is more uniform for the single crystals with 0° lamellar orientation, since they have more homogeneous microstructure and smaller difference in the hardness between the two phases. Our findings are useful to promote the applications and design of new TiAl-based single crystals as structural materials, from the perspective of the microstructure and micro-mechanical properties.

The effects of casting currents on the thermophysical behaviors, atomic and nanoscale structure, and mechanical properties of two Zr-based-bulk metallic glasses, i.e., Zr59Cu33Al8 and Zr59(Cu0.55Fe0.45)33Al8, were studied by using differential scanning calorimetry, wide-angle X-ray diffraction, and small-angle X-ray scattering, as well as compression tests. The casting currents can be tuned to change the casting initiative temperature. Results revealed that there is no anomalous structural change for the Zr59Cu33Al8 molten liquid before crystallization during cooling with different casting currents. In contrast, liquid-state phase separation was suggested to occur in the Zr59(Cu0.55Fe0.45)33Al8 molten liquid prepared using lower casting current before crystallization during cooling. The position shift of the first sharp diffraction peak for the diffraction pattern of Zr59(Cu0.55Fe0.45)33Al8 shows that the density of the molten liquid may decrease upon cooling at different casting currents. The small-angle X-ray scattering results indicate that the heterogeneity of the Zr59(Cu0.55Fe0.45)33Al8 metallic glasses increases with decreasing the casting temperature. As a result, the metallic glasses with a liquid-state phase separation possess better mechanical properties, including higher-yielding stress and more significant compressive ductility. The increase in degree of heterogeneity formed by nanoscale liquid-state phase separation and their interactions with the shear bands for the Zr–Cu–Fe–Al bulk metallic glasses were suggested to be responsible for the enhanced mechanical properties.

Fe-based bulk metallic glasses (BMGs) have attracted great attention due to their excellent soft magnetic properties and high fracture strength, but few applications have been materialized as structural materials because of their brittleness at room temperature. Here, we successfully synthesized an Fe39Ni39B14.2Si2.75P2.75Nb2.3 BMG which exhibits large plastic strain of 7.8%, high fracture strength of 3.35 GPa and excellent soft magnetic properties, i.e., rather high saturation flux density of 0.88 T, low coercive force of 0.7 A/m and high permeability of 20800. The results indicated that the mutual repulsion between ductility and strength could be renovated in the Fe-based BMGs by the rearrangement of atomic configurations through Ni addition. With proper combination of non-directional metal-metal bonds and directional metal-metalloid bonds, the mechanical properties of FeNi-based BMGs can be improved. Our studies provide a guideline in designing ductile FeNi-based BMGs with high strength, large GFA and excellent soft magnetic properties.

The multiplication and interaction of self-organised shear bands often transform to a stick-slip behaviour of a major shear band along the primary shear plane, and ultimately the major shear band b...

A novel ductile [(Co0.7Fe0.3)0.68B0.219Si0.051Nb0.05]99.5Cu0.5 bulk metallic glass (BMG) with the strength of 4.4 GPa and the compressive plastic strain of 2.5% was successfully synthesized in this work. We found, by adding tiny Cu (0–0.9 at. %) element, both the plasticity and the saturation magnetization of CoFeBSiNb BMGs can be improved, which is attributed to the existence of ferromagnetic and ductile α-(Fe, Co) nanoparticles in the glass matrix. The abundant of vein patterns and high-density multiple shear bands were observed on the fracture surface of Cu-added Co-based bulk glassy rods. The reason for these results is that the nanoscale particles hinder the propagation of the shear band, promote the generation of multiple shear bands and enhance the plasticity. Our investigations shade a light on understanding the nano-scale precipitation phase enhanced ductility mechanism in high strength BMGs such as Fe- and Co-based BMGs and lead a map for finding new high strength BMGs with high plasticity.