Plasticity Of Glasses Research Articles

RESEARCH ON OPTIMIZATION OF INDUSTRIAL BUILDING FACADES INTEGRATING WITH PHOTOVOLTAIC POWER

Industrial buildings are important production carriers in urban space, but they also have problems such as high production energy consumption, serious environmental pollution, and poor built interface, which have attracted much attention. Building environment optimization and energy structure adjustment have become the focus of industrial building research. In the context of the national carbon neutral policy, this paper studies the impact of industrial buildings on the urban environment, combines photovoltaic power generation technology, explores the integrated design strategy of CdTe generation glass and industrial building facades, and uses the southwest cement plant project in Lijiang, Yunnan as an example, a practical study was carried out, aiming to use industrial building facade resources to improve the aesthetics and functionality of the building facade at the urban interface of the park. Research shows that the strong plasticity of CdTe photovoltaic glass can not only provide necessary power energy for industrial buildings and optimize the building's energy structure, but its color and material ductility can also improve the aesthetics of industrial building facades. This article provides certain reference and reference significance for subsequent related research.

Modulating the rejuvenation in a Al75Mg25 metallic glass by multiple recovery annealing treatment

Rejuvenation presents a promising way to improve the plasticity of metallic glasses. How modulating the degree of rejuvenation of metallic glasses remains a challenging issue. Here, based on the molecular dynamics simulation, we investigate the evolution of the structural and mechanical properties of a binary Al75Mg25 metallic glass and successfully realized the rejuvenation modulation through the multiple recovery annealing treatment. A range of samples with different degrees of rejuvenation were obtained by successive multiple recovery annealing process. According to our calculations, we found that the degree of rejuvenation is highly correlated with the Al-centered clusters. Microstructural analyses show that a higher degree of rejuvenation is concomitant with less 1551 index of Honeycutt-Andersen indices and a lower content of <0,0,12,0 > in terms of Voronoi Tessellation analysis. Moreover, our calculated results demonstrate that the samples with the aging initial state show a higher degree of rejuvenation as compared to the samples with the rejuvenated initial state. This can be attributed to that there are more icosahedral clusters, which are more likely to change to other types of clusters with low local fivefold symmetry in the aged samples during the subsequent high-temperature annealing process. Our work confirms that proper multiple (no more than three times) recovery annealing treatment can increase the degree of rejuvenation of metallic glasses and can offer a better understanding of the effect of rejuvenation on the microstructures and mechanical properties of metallic glasses.

Strengthening effects of indentation notches on metallic glasses and their sensitivity to stress triaxiality

In this study, a metallic glass sample with an annular indentation notch was successfully constructed by a compression rod cyclic compression strategy using molecular dynamics simulation, and the mechanical behaviors of cut-notched metallic glass samples with the same stress triaxiality and notch size under triaxial compression were comparatively analyzed. It is found that the indentation notch further improves the strength and plasticity of the metallic glass, while it is insensitive to the cut-notched metallic glass with the same notch size. During triaxial compression, rejuvenation and shear softening lead to an increase in free volume, while diffusion and residual compressive stresses lead to a decrease in free volume. The stress triaxiality plays a key regulatory role in their competition and affects the final state of free volume change. This study provides a new theoretical basis and process idea for the enhancement of strength and plasticity of metallic glass.

Enhancing the Energy State and Plasticity of Relaxed Cu49Hf42Al9 Bulk Metallic Glass by Rejuvenation

Enhancing the Energy State and Plasticity of Relaxed Cu49Hf42Al9 Bulk Metallic Glass by Rejuvenation

Unravelling the relation between free volume gradient and shear band deflection induced extra plasticity in metallic glasses

Previous experiments have revealed that the controllable introduction of structural gradients in metallic glasses (MGs) can endow the materials with extra plasticity due to the gradient-induced deflection of shear bands. However, the relation between the spatial structural gradient and the initiation of shear band deflection remains unclear. The current study has been focused on investigating the relationship between the improved mechanical properties of MGs and structural gradients specified by the distribution of the intrinsic free volume. Molecular dynamics (MD) simulations are firstly performed on homogeneous MG models containing various initial free volume values, showing that the shear band angle increases with decreasing free volume under uniaxial compression, whereas higher shear band angle is observed under uniaxial tension with increasing free volume. Based on the asymmetric behaviors of MGs under compression and tension, a theoretical model is developed to quantitatively characterize the influence of free volume on the mechanical response of MGs, which incorporates a failure criterion based on free volume generation during external loadings. The model can be further utilized to interpret and predict the fracture strain, shear band angle, maximum stress, and fracture surface morphology of gradient structured MGs in both simulations and experiments. The relationship between free volume gradient and shear band deflection induced extra plasticity established in this study provides valuable guidance for the structural design of MGs with enhanced mechanical properties.

How to catch a shear band and explain plasticity of metallic glasses with continuum mechanics

Capturing a shear band in a metallic glass during its propagation experimentally is very challenging. Shear bands are very narrow but extend rapidly over macroscopic distances, therefore, characterization of large areas at high magnification and high speed is required. Here we show how to control the shear bands in a pre-structured thin film metallic glass in order to directly measure local strains during initiation, propagation, or arrest events. Based on the experimental observations, a model describing the shear banding phenomenon purely within the frameworks of continuum mechanics is formulated. We claim that metallic glasses exhibit an elastic limit of about 5% which must be exceeded locally either at a stress concentrator to initiate a shear banding event, or at the tip of a shear band during its propagation. The model can successfully connect micro- and macroscopic plasticity of metallic glasses and suggests an alternative interpretation of controversial experimental observations.

Simultaneous improvement in surface quality and hardness of laser shock peened Zr-based metallic glass by laser polishing

Laser shock peening (LSP) is an effective method to improve the plasticity of metallic glasses (MGs) but it also deteriorates the surface quality and decreases the surface hardness, which in turn hinders the applications of MGs. Accordingly, this study was attempted to achieve the simultaneous improvement in surface quality and hardness of LSPed Zr-based MG by nanosecond pulsed laser polishing. LSP of the MG was firstly performed by using a high-energy pulsed laser to prepare the LSPed MG samples, and then laser polishing of the LSPed MG surface was conducted by using nanosecond pulsed laser. The effects of laser polishing parameters (i.e., average laser power, scanning speed, overlap rate, and number of irradiation cycle) on the surface quality and hardness of the LSPed MG were investigated in detail. The experimental results showed that after laser polishing under specific conditions, a 90% reduction in surface roughness and a 11 % increase in surface hardness could be achieved for the LSPed MG surface. This study provides a simple and effective method to simultaneously improve the surface quality and hardness of LSPed MGs, which would be of great significance for the practical engineering applications of MGs.

Structural heterogeneity and plasticity of a Zr-based metallic glass modulated by high-temperature deformation

Metallic glasses (MGs) are of high strength but limited plasticity at room temperature (RT) due to localized shear in the intrinsically heterogeneous structure. Here, we investigate the variation of structural heterogeneity and plasticity of a Zr-based MG after high-temperature (T) tension under different stresses (σ) at 579 K (0.9Tg, where Tg is the glass transition temperature). The correlation length (ξ) of the heterogeneous structure and the average Young's modulus (E¯) increase with σ when σ is below 160 MPa; when σ exceeds 160 MPa, both ξ and E¯ decrease with σ, leading to the improvement of the plasticity. This research could be enlightening for improving the plasticity of MGs at RT through tuning their structural heterogeneity with high-T deformation.

Elementary processes in dilatational plasticity of glasses

Materials typically fail under complex stress states, essentially involving dilatational (volumetric) components that eventually lead to material decohesion/separation. It is therefore important to understand dilatational irreversible deformation—i.e., dilatational plasticity—en route to failure. In the context of glasses, much focus has been given to shear (volume-preserving) plasticity, both in terms of the stress states considered and the corresponding material response. Here, using a recently developed methodology and extensive computer simulations, we shed basic light on the elementary processes mediating dilatational plasticity in glasses. We show that plastic instabilities, corresponding to singularities of the glass Hessian, generically feature both dilatational and shear irreversible strain components. The relative magnitude and statistics of the strain components depend both on the symmetry of the driving stress (e.g., shear versus hydrostatic tension) and on the cohesive (attractive) part of the interatomic interaction. We further show that the tensorial shear component of the plastic strain is generally nonplanar and also extract the characteristic volume of plastic instabilities. Elucidating the fundamental properties of the elementary micromechanical building blocks of plasticity in glasses sets the stage for addressing larger-scale, collective phenomena in dilatational plasticity such as topological changes in the form of cavitation and ductile-to-brittle transitions. As a first step in this direction, we show that the elastic moduli markedly soften during dilatational plastic deformation approaching cavitation. Published by the American Physical Society 2024

Absence of ultrasonic-vibration-induced plasticity in metallic glacial glasses

Absence of ultrasonic-vibration-induced plasticity in metallic glacial glasses

Cryogenic thermal cycling induced simultaneous improvement of strength and ductility in a Zr-based bulk metallic glass composite

Preparing bulk metallic glass composites (BMGCs) is an effective way to improve the plasticity of bulk metallic glasses (BMGs). However, the enhancement of plasticity is usually at the cost of deterioration in strength. In this study, a series of BMGCs with the nominal composition of Zr48Cu48Al4 was prepared. Finely dispersed B2 CuZr crystals are embedded in a glassy matrix and subsequently, these composites were cryogenically cycled in liquid nitrogen followed by heating to various temperatures below the glass transition temperature. It was found that the samples after cryogenic thermal cycling (CTC) treated at an intermediate upper temperature shown a simultaneous improvement of yielding strength from 1680 MPa to 1832 MPa and plasticity from 5.6% to 9.1%. The enhancement of yielding strength is ascribed to the existence of the B19′ phase resulted from the partial martensitic transformation during the CTC treatment, while the improvement of plasticity is attributed to the higher free volume content and the larger “blocking effect” from the B19’ after the samples were treated by CTC. The combination of CTC treatment and precipitation of crystals provides a new strategy for improving the mechanical properties of the BMGs.

In situ TEM study of pulse-enhanced plasticity of monatomic metallic glasses

The electropulsing process can be used to tailor the microstructure and deformability of metallic glasses (MGs). Here, we report the microstructural origin of enhanced electroplasticity of monatomic Ta MG nanowires. Under electromechanical loading, the Ta MG nanowire exhibits improved ductility and obvious necking behavior. By evaluating the dynamic structural evolution via in situ diffraction, it is found that the atomic mobility in flow units of Ta MG can be improved significantly under the stimulation of pulse current, mainly through the athermal electron-atom interaction, which results in the fast annihilation of flow units and, thereby, fast structural relaxation. These structural evolution processes can help to eliminate the formation of the obvious shear band. These findings provide insight into the origin of electroplasticity in amorphous materials, which is of scientific and technological significance for the design and processing of a variety of MGs.

Atomic-scale structures determining the plasticity of metallic glasses viewed from the icosahedral medium-range orders and its spatial distribution

In the study of metallic glasses, the characterization of free volumes and icosahedral clusters has been a longstanding approach to understanding plasticity. However, recent research has illuminated the limitations of exclusively relying on these factors to explain the plastic deformation of metallic glasses. To address this limitation, we have introduced the concept called the h-value in a prior study, which quantifies the spatial distribution of disrupted interpenetrating connections of icosahedra and provides insights into how minor elements influence the deformation behavior of metallic glasses. However, the h-value was only employed on Cu50Zr50, Cu47.5Zr47.5Al5, and (Cu0.5Zr0.5)100-xAgx alloys and provided insight into the correlation between the spatial distribution of icosahedra and plasticity, but it is needed to be validated on a wider range of alloys to confirm the applicability of the h-value. In this study, we utilize a Cu–Zr binary amorphous system, known for its compositional diversity and corresponding wide range of plasticity, to validate and benchmark our approach against experimental results. Our findings underscore the robustness of the h-value as a structural descriptor, representing the degree of spatial distribution within the local structural basis. This metric holds promise as a valuable tool for determining the plasticity of metallic glasses.

Dependence between glass transition and plasticity in amorphous aluminum oxide: A molecular dynamics study

Aluminum oxide (Al2O3) is known to form amorphous structures that exhibit a unique plastic deforming ability at room temperature. However, alumina is considered a poor glass former, and it has been unclear whether alumina undergoes a glass transition during solidification from melt, and what effects such a transition would have on the plastic deform ability of the material. Here, we show using molecular dynamics simulations that a melt-quenched alumina indeed exhibits a glass transition, and that the glass transition greatly affects the observed material ductility. The glass transition temperature is found to positively correlate with the used cooling rate and we observe that maximum stress correlates with varying quench cooling rates in tensile test simulations, indicating that profound structural differences are formed during the glass transition. Significantly, we show that inducing plastic deformation allows erasing the structural memory of the material, and at 50% strain, all samples quenched at different rates shift again to exhibit similar flow stress. Characterizing methods that include medium-range structural information show a better ability to capture the structural differences formed during the glass transition. Our analysis results indicate that lower glass transition temperature imposes deeper potential wells of atoms and, therefore, a ’colder’ structure. The mechanical work input plays a similar role as input thermal energy to the structure. A ’colder’ structure needs more mechanical energy to get activated, thus showing a higher maximum stress. At a steady state flow, all samples show similar flow stress, indicating a similar structure.

Extreme rejuvenation of a bulk metallic glass at the nanoscale by swift heavy ion irradiation

Swift heavy ions can be used as a tool to tune material properties by generating high aspect ratio, nanometric trails of defects, or new disordered phases. This work explores different aspects of using this tool for rejuvenating and enhancing plasticity in bulk metallic glasses. An amorphous alloy with a nominal composition of Pd40Ni40P20 was irradiated with GeV-accelerated Au ions. Irradiation-induced out-of-plane swelling steps up to approximately 100 nm in height are measured at the boundary between irradiated and non-irradiated areas. Changes of the relaxation enthalpy have been investigated using differential scanning calorimetry. Low-temperature heat capacity measurements substantiate an irradiation-induced increase of the boson peak height with increasing fluences. Accompanying transport measurements using radioactive Ag atoms as tracer also revealed increased diffusion rates in the irradiated samples dependent on the total fluence. Nano-indentation measurements show enhanced plasticity in the ion-irradiated glass which can be correlated with an increased heterogeneity as indicated by variable resolution fluctuation electron microscopy. The whole volume of the derived data substantiates a prominent enhancement of the excess volume in the solidified ion tracks and the irradiation-induced modifications are discussed and analyzed in the framework of strong glass rejuvenation within the nanometric ion tracks.

Cryogenic thermal cycling effects on serration behavior in wide glass transition temperature Zr-based bulk metallic glasses

Serration behavior serves as a pivotal link connecting micro-deformation mechanism to the mechanical properties of metallic glasses. To elucidate the impact of cryogenic thermal cycling (CTC) and compositional modifications on metallic glasses’ serration behavior, a series of Zr-based metallic glasses, exhibiting a broad range of glass transition temperatures (Tg), were meticulously manufactured. The stress drop magnitude initially decreases before the peak-rejuvenation induced by CTC, then gradually increases, while the number of stress drops exhibits an initial increase and then a decrease. These trends correlate with optimized plasticity of the metallic glasses. Remarkably, metallic glasses with lower Tg predominantly undergo strain hardening during plastic deformation. They exhibit lower viscosity in shear band zones and stress drop compared to others, attributed to the temperature increase around shear band zones approaching Tg. This phenomenon promotes shear band activation in smaller flow units, leading to finer serrations compared to glasses with higher Tg.

Distinct avalanche dynamics detected in metallic glasses with high energy state revealing the crack-like shear banding mechanism

When a sufficiently high stress is applied to a metallic glass, causing plastic deformation, the material undergoes structural reconfiguration through dissipative slip avalanche events that release local stresses. By utilizing isothermal annealing and cold rolling techniques to tune the energy levels of metallic glasses, it has been observed that structural rejuvenation is accompanied by structural relaxation, as evidenced by distinct changes in avalanche dynamics. We present detailed statistics of the avalanche dynamics during shear band formation in energy-tuned metallic glasses, ranging from structurally relaxed to rejuvenated states. By analyzing shear band characteristics and examining scaling exponents, avalanche durations, and stress relaxation rates, we can establish a connection between the local activation of shear transformation zones and the formation of macroscopic shear bands. The statistics of avalanche duration indicate that an increase in soft zones within metallic glasses can alleviate stress release and stabilize plastic flow, as evidenced by the characteristics of shear bands. We attribute the significant transition of serrated flow, observed at different energy levels (i.e., as-cast, relaxed, and rejuvenated states) to the variations in nucleation and multiplication of shear bands that originate from local weak spots. Analysis of the distinct avalanche dynamics suggests that in lower energy level metallic glasses, the nucleation and propagation of shear bands exhibit localized crack-like behavior, while in higher energy level metallic glasses, they display diffused crack-like characteristics. Indeed, our results strongly support that the decreased avalanches observed in the high energy level metallic glasses originate from the nucleation of numerous small shear bands, which directly compete with the propagation of the main local shear band. These findings deepen our fundamental understanding of the relationship between the microscopic mechanism of slip avalanche dynamics and shear banding, providing a pathway to control the plasticity of metallic glasses.

An order of magnitude enhancement in ductility of a metallic glass of peak rejuvenation

Exceptional ductility has been a long-sought-after property of metallic glasses, and cryogenic thermal cycling rejuvenation has been actively explored to enhance the plasticity of metallic glasses. By tuning the holding time and number of cycles of cryogenic thermal cycling processing, we here report a (Zr0.8125Cu0.1875)79Ni10Al10Nb1 metallic glass of peak rejuvenation with the plasticity of an order of magnitude higher than that of the as-cast glass, without sacrificing its strength. Characterizations indicate that the loose atomic packing of the metallic glass of peak rejuvenation facilitates the generation and proliferation of shear bands in the early stage of plastic deformation, and the resultant dense shear bands tend to be deflected due to their interaction with each other and/or structural inhomogeneity in the matrix, hindering their rapid propagation and in turn increasing the plasticity. The combination of high relaxation enthalpy and high plasticity obtained here is outstanding from the previous rejuvenated metallic glasses which have either high relaxation enthalpy or high plasticity, while never both. This work identifies an alloy system with very high efficiency in plasticity improvement through cryogenic thermal cycling rejuvenation and represents a promising guide for improving the plasticity of metallic glasses.

Structural Relaxation, Rejuvenation and Plasticity of Metallic Glasses: Microscopic Details from Anelastic Relaxation Spectra

The lack of periodicity and long-range order poses significant challenges in explaining and modeling the properties of metallic glasses. Conventional modeling of nonexponential relaxation with stretched exponents leads to inconsistencies and rarely offers information on microscopic properties. Instead, using quasi-static anelastic relaxation, we have obtained relaxation-time spectra over &gt;10 orders of magnitude of time for several metallic glasses. The spectra enable us to examine in microscopic detail the distribution of shear transformation zones and their properties. They reveal an atomically-quantized hierarchy of shear transformation zones, providing insights into the effect of structural relaxation and rejuvenation, the origin of plasticity and the mechanisms of the alpha and beta relaxation.

Tuning dynamic mechanical properties of Cu50Zr50 nanoglasses/ nanopolycrystalline Cu composites investigated by molecular dynamics simulation

Nanoglasses/nanopolycrystalline (NGNP) composites have emerged as a promising approach to balance the strength and plasticity of metallic glasses. Herein, the shock responses of five Cu50Zr50 NGNP composites are investigated via molecular dynamics simulations under a shock velocity of 0.5 to 2.0 km/s. The simulation results reveal that with an increasing fraction of nanocrystalline grains, the Hugoniot pressure, shear stress, and spall strength of the composites are enhanced, while their atomic strain decreases under shock loading. Additionally, due to the dominant structure type changes from an amorphous structure to a crystal structure, the deformation mechanism transforms from the growth of shear transformation zones to dislocation slip, phase transition, and amorphization as the impact velocity increases. In terms of the spallation, the spall strength of the composites rises initially and then declines due to the competing mechanisms of strain rate hardening and shock-induced softening.