Shear Band Formation Research Articles

Delamination behaviour and surface morphology of wholly thermoplastic composites using different ultra-high molecular weight thermoplastic fabrics with pristine and toughened Elium resin under Mode I loading

Current research investigates the manufacturing and bonding characteristics of wholly thermoplastic composites with thermoplastic fibres and acrylic Elium® resin and toughened Elium®IM with 10% weight acrylonitrile butadiene styrene (ABS) particles under Mode I loading. Ultra-high molecular weight polypropylene (UHMWPP)/Elium® IM and UHMWPP/Elium® composites have shown 43.9% and 24.5% higher critical energy release rate compared to epoxy composite systems, while a similar trend was observed in the case with composites with polyester as the reinforcement system. For ultra-high molecular weight polyethylene (UHMWPE)/Elium®, the increase was only 13.7% but with the use of toughened thermoplastic variant, the increase was found to be 36.8% higher. Detailed microscopic examination reported fibre bridging, pull-out, strong fibre–matrix adhesion, riverlines, and matrix deformation owing to the ductile characteristic of Elium® resin. ABS-modified Elium®IM composites have shown rough matrix fracture surface and there was internal cavitation of ABS particles followed by crack growth and local shear band formation.

Coupled microscopic and micromagnetic depth-specific analysis of plastic deformation and phase transformation of metastable austenitic steel AISI 304L by flow forming

Abstract This paper presents the characterization of the microstructure evolution during flow forming of austenitic stainless steel AISI 304L. Due to plastic deformation of metastable austenitic steel, phase transformation from γ-austenite into α’-martensite occurs. This is initiated by the formation of shear bands as product of the external stresses. By means of coupled microscopic and micromagnetic investigations, a characterization of the microstructure was carried out. In particular, this study shows the distribution of the strain-induced α’-martensite and its influence on material properties like hardness at different depths. The microstructural analyses by means of electron backscattered diffraction (EBSD) technique, evidence a higher amount of α’-martensite (ca. 23 %) close to the outer specimen surface, where the plastic deformation and the direct contact with the forming tool take place. In the middle area (ca. 1.5 mm depth from the outer surface), the portion of transformed α’-martensite drops to 7 % and in the inner surface to 2 %. These results are well correlated with microhardness and micromagnetic measurements at different depths. EBSD and atomic force microscopy (AFM) were used to make a detailed characterization of the topography and degree of deformation of the shear bands. Likewise, the mechanisms of nucleation of α’-martensite were discussed. This research contributes to the development of micromagnetic sensors to monitor the evolution of properties during flow forming. This makes them more suitable for closed-loop property control, which offers possibilities for an application-oriented and more efficient production.

Combined Tension-Shear Failure of Ductile Materials

Failure of ductile materials is usually expressed in terms of effective plastic strain. Ductile materials can fail by two different failure modes, shear failure and tensile failure. Under dynamic loading, shear failure has to do with shear localization and formation of adiabatic shear bands. In these bands plastic strain rate is very high, dissipative heating is extensive, and shear strength is lost. Shear localization starts at a certain value of effective plastic strain, when thermal softening overcomes strain hardening. Shear failure is therefore represented in terms of effective plastic strain. On the other hand, tensile failure comes about by void growth under tension. For voids in a tension field there is a threshold state of the remote field for which voids grow spontaneously (cavitation) and the material there fails. Cavitation depends on the remote field stress components and on the flow stress. In this way failure in tension is related to shear strength and to failure in shear. Here, we first evaluate the cavitation threshold for different remote field situations, using 2D numerical simulations with a hydrocode. We then use the results to compute examples of rate dependent tension-shear failure of a ductile material.

Yielding, shear banding, and brittle failure of amorphous materials

Widespread processes in nature and technology are governed by the dynamical transition whereby a material in an initially solid-like state then yields plastically. Major unresolved questions concern whether any material will yield smoothly and gradually (ductile behaviour) or fail abruptly and catastrophically (brittle behaviour); the roles of sample annealing, disorder and shear band formation in the onset of yielding and failure; and, most importantly from a practical viewpoint, whether any impending catastrophic failure can be anticipated before it happens. We address these questions by studying the yielding of slowly sheared athermal amorphous materials, within a minimal mesoscopic lattice elastoplastic model. Our contributions are fourfold. First, we elucidate whether yielding will be ductile or brittle, for any given level of sample annealing. Second, we show that yielding comprises two distinct stages: a pre-failure stage, in which small levels of strain heterogeneity slowly accumulate, followed by a catastrophic brittle failure event, in which a crack quickly propagates across the sample via a cooperating line of plastic events. Third, we provide an expression for the slowly growing level of strain heterogeneity in the pre-failure stage, expressed in terms of the macroscopic stress-strain curve and the sample size, and in excellent agreement with our simulation results. Fourth, we elucidate the basic mechanism via which a crack then nucleates and provide an approximate expression for the probability distribution of shear strains at which failure occurs, as determined by the disorder inherent in the sample, expressed in terms of a single annealing parameter, and the system size.

New double surface constitutive model of intermittent plastic flow applied to near 0 K adiabatic shear bands

One of the most interesting phenomena that occur in ductile materials strained in the proximity of absolute zero are the adiabatic shear bands. In the stainless steels, massively used to construct superconducting magnets, their occurrence can be detected by various techniques, including magnetometric methods (feritscope). Formation of adiabatic shear bands is strictly correlated to the occurrence of the intermittent plastic flow (IPF), characteristic of stainless steels strained in liquid or superfluid helium. Evidence for the occurrence of the phase transformation during nucleation and formation of the shear bands in the proximity of absolute zero is for the first time given. The rate of shear bands propagation along the sample as well as the amount of secondary phase is measured. In order to describe the intermittent plastic flow, novel double surface model has been developed. It includes type Huber-Mises-Hencky yield surface, and new recovery surface reflecting the lower bound for the stress oscillations. The yield surface can move and expand due to nonlinear mixed (kinematic and isotropic) hardening, resulting from the phase transformation, whereas, the recovery surface remains constant. The serrations occur between the yield surface and the recovery surface, with the yield surface coming back to its initial position after each serration. Each serration corresponds to formation of single shear band there, where the easy slip planes are available, and the mechanism of anchoring the shear bands by the secondary phase is explained. New double surface model has been correlated to the experimental data and applied to explain stress oscillations during the regular stage of the intermittent plastic flow, when the shear bands gradually cover the gauge length of the sample.

Effects of deformation-induced martensitic transformation on quasi-static and dynamic compressive properties of metastable SiVCrMnFeCo high-entropy alloys

High-entropy alloys (HEAs) utilizing a deformation-induced martensitic transformation (DIMT) mechanism have been developed as they exhibit an excellent balance of strength, ductility, and toughness. Investigations on deformation behaviors under dynamic responses are essential for their wide and reliable cryogenic applications; however, the effects of DIMT on mechanical properties under dynamic and cryogenic environments have hardly been studied yet, especially in metastable HEAs. In this study, compressive properties of two SiVCrMnFeCo alloys having different initial microstructure and stability of face-centered-cubic (FCC) against the DIMT were investigated under both quasi-static and dynamic loadings and at room and cryogenic temperatures. Under dynamic loading, the extent of DIMT was reduced than that under quasi-static loading due to the increased adiabatic heating, which increased the stability of FCC and suppressed the DIMT behavior. Nevertheless, the activated DIMT with decreasing stability of FCC due to the increased Si content and the decreased test temperature enhanced overall compressive properties. However, the interrupted dynamic compressive test results showed that the shear localization and the formation of adiabatic shear band (ASB) were promoted as the martensite formed more by the DIMT, concurrently resulted in the deterioration of resistance to shear cracking. These findings suggest that the delicate control of stability of FCC would be significant in wide and effective applications of the metastable alloys toward cryogenic or dynamic environments.

Formation of η-oriented shear bands and its significant impact on recrystallization texture in strip-cast electrical steel

The evolution of shear band (SB) and texture in strip-cast electrical steel was studied in order to investigate the crystallographic character of SB and its influence on recrystallization texture. Shear deformation in the form of SB played an effective role in tailoring the local lattice rotation to accommodate heavy deformation in the case of inhomogeneous deformation under conditions of initial coarse grain in strip-cast electrical steel. During rolling process, η-oriented SBs appeared at different stages of deformation as a result of geometric softening. Cube-oriented SB was mainly retained from initial exact Cube grain at early stage of shear deformation and Goss-oriented SB was newly developed during the formation of γ-fiber matrix after heavy deformation. {210}<001> SB formed as a transition form among different SBs. Crystal rotation inside SB, SB dimension and SB boundary misorientation progressed in proportion to cold rolling reduction. It is demonstrated that crystallographic direction of SBs tended to be parallel to <001> under the driving force of reduction in stored energy to maintain relatively quasi-stable state. Low orientation gradient as well as relatively low density of dislocations was developed within SB region, while high orientation gradient formed between SB region and surrounding matrix. Interestingly, the η-oriented cell blocks inside SBs provided preferential nucleation sites for Goss and Cube texture at early stage of recrystallization, which significantly contributed to beneficial recrystallization texture in a manner of texture inheritance and superior magnetic properties (B50 was as high as 1.81 T, and P1.5/50 was as low as 4.0 W/kg).

Wear mechanisms description in nanoscale by SEM/TEM of multilayer Zr/ZrN coatings in dependence on phases ratio.

As a result of loading with an external force during the wear process, coating deforms uniformly. After a certain limit load is exceeded, coating deformation is localised through the formation of the so-called shear bands. It has been showed experimentally the process of shear bands formation. The microstructural characterisation before and after the mechanical tests was performed using scanning and transmission electron microscopy (SEM and TEM) on cross-sections of the samples. The analysis indicated that in the case of multilayer coatings where the ratio of the metallic to the ceramic phase is 1:1, the shear bands are formed at an angle of 45°. With a greater proportion of the ceramic phase to metallic (ratio 1:2), the shear band changed the shear angle from ∼45° to ∼90°. Mechanical in situ tests were carried out in the chambers of SEM and TEM. The scratch tests in the SEM were done with the simultaneous observation of the phenomena occurring on the surface of the tested materials showed that at a scratch force of 0.04 N, the additional outer a-C:H layer was damaged, which was shown in the form of a fault in the force-displacement diagram, and in the form of splits visible in the SEM image. However, the application of this additional layer had a positive effect on the wear mechanism of the entire coating structure. The test also indicated that in the case of coatings with phases ratio 1:2 and 1:4 (metallic to ceramic), the characteristics of the brittle material were demonstrated, unlike the coating with a 1:1 phase ratio, where plastic properties predominated. However, for the 1:2 phase ratio coating, the chip was more ductile than for the chip formed when testing a 1:4 phase ratio coating. For in situ mechanical testing in the TEM, a straining holder was used. The test showed that the shear band angle for a 1:1 ratio coating has changed from 45° to 90° due to the different direction of force interaction.

Comparative Studies on Shear Failure Behaviors of U71Mn Rail Steel at High Strain Rates Using Hat-Shaped Specimens

Abstract The shear failure behaviors of U71Mn rail steel are investigated by quasi-static and dynamic compression tests utilizing two different hat-shaped specimens: S1 which combines shear and compressive stress states and S2 which combines shear and tensile stress states. A split Hopkinson pressure bar is used to acquire shear stress–strain curves at various initial temperatures and shear strain rates, and it is found that a lower shear strain rate is observed in hat-shaped specimen S1 than that in hat-shaped specimen S2 under the same impact pressure. Scanning electron microscopy is employed for observing the microstructures of specimens. The results indicate that the hat-shaped specimen S1 is difficult to form voids and dimples. Moreover, as far as the hat-shaped specimen S2 is concerned, the number of voids reduces with the rising shear strain rate, and no voids appear on the fracture surface at the shear strain rate of 36,000 s−1. Furthermore, the creation of voids is aided by a rise in initial temperature. The factors affecting the formation of adiabatic shear bands are explored based on the numerical simulation, which suggests that the magnitude of the temperature gradient plays a crucial role in the generation of adiabatic shear bands.

Microstructure and texture evolution of nonoriented silicon steel during the punching process

The iron core of a motor is mainly manufactured from rolled nonoriented silicon steel using a punching process that leads to deformation and texture evolution at the cutting edge. According to this process, circular samples of nonoriented silicon steel were prepared by punching using blunt punch tools. In this work, two positions along the rolling and transverse directions at the cutting edge were analyzed. The main mechanisms of deformation for both positions are dislocation slip and formation of shear bands. These two mechanisms lead to similar texture evolutions for both positions. The dislocation slip leads to the formation of the {221} 〈uvw〉 component in the unbending area (200 µm away from the cutting edge) and intermediate continuum-bent area. Additionally, the evolution of the texture from the {111} γ fiber to the {110} fiber was observed at the extremity of the cutting edge with the formation of shear bands.

Gradient-enhanced modelling of deformation-induced anisotropic damage in metallic glasses

Recent experimental and computational studies at different scales reveal an apparent flow-induced anisotropy of the inelastic deformation behaviour in metallic glasses (MGs). However, the anisotropic damage behaviour accompanied by the formation of shear bands is not adequately described in the previous constitutive modelling work. In this study, we develop a thermodynamically-consistent, anisotropic damage model incorporating tension–compression asymmetry (TCA) to describe the unique deformation and damage behaviours. The elastic–plastic response, including the normal stress sensitivity and the plastic dilatancy, is captured by the extended Mohr–Coulomb criterion. A second-order damage tensor is adopted for describing the anisotropic damage behaviour of MGs. By augmenting the Helmholtz free energy function to be dependent on the gradient of the free volume concentration and the gradient of the nonlocal damage parameter, the kinetic equations for the corresponding internal variables are derived within the framework of finite deformation continuum thermodynamics. Different material degradations under tension and compression are considered by decomposing the elastic strain tensor into a positive mode and a negative mode in the free energy function, where the tension-strain-induced damage is fully switched on while the compression-strain-induced damage is only partially activated. The influence of the TCA parameter on the damage initiation, crack propagation and shear bands density, as well as the influence of the gradient regularisation parameter on the width of the damage zone, are systematically studied. The proposed damage model is validated by experiments carried on unnotched and notched microcantilever beams. The simulation results show that both the displacement–load curves and the shear band patterns are in good agreement with the experimental observations.

Effect of stress triaxiality on plastic deformation of metallic glasses

Aiming at fabrication of cellular metallic glasses with high mechanical properties, double edge notched samples were designed by orthogonal design method. Compressive tests on those samples were carried out to investigate mechanical responses induced by different notch settings. It was found that the notch tip distance and stress triaxiality are two key factors controlling yield strength and plasticity of notched samples. Besides, free volume theory factoring in hydrostatic stress was incorporated into finite element model to simulate shear band (SB) deformation process for different samples. Combined with experiments, simulations as well as microstructure observations, it was concluded that the notch tip distance effect could be ascribed by transition process between sparsely-intersected and densely-intersected SBs, and the later is the key to plasticity enhancement. Additionally, large stress triaxiality could improve the global plasticity by introducing densely-intersected SBs so as to hinder sample from fracturing along one major SB. The current work could offer useful data in providing direct evidence on fabrication of cellular materials as well as enriching shear band formation mechanism of monolithic metallic glasses.

Predictive model of chip segmentation in machining of high-strength metallic alloys

Chip segmentation is the dominant chip formation mechanism during the machining of high-strength metallic alloys which directly affects the machining productivity and the final product’s quality. This paper investigates the mechanism of shear band formation and its contact with the cutting tool for different titanium and nickel alloys. First, we reveal that the shear bands are in direct contact with the cutting tool due to rolling on its rake face, although the contact mechanism is different for titanium and nickel alloys. In addition, the effect of the stored energy at the tool-chip interface, which is believed to be the reason for chip segmentation in some studies, is investigated theoretically. We found that the stored energy at the tool-chip interface affects the strain rate temporarily and has minimal impact on the chip segmentation. Moreover, we provide a theoretical prediction of the workpiece material’s displacement, its distribution, and degree of segmentation for the first time without any post-mortem analysis of the produced shear bands. To this end, the rolling process must be taken into account for accurate prediction. We show that the segmented chip’s displacement can be accurately predicted without any fracture criterion since the shear band itself is a type of ductile material failure. It is shown that the shear bands can accommodate large strains (for example, around 45 when cutting Ti-6Al-4V at 60 m min−1 cutting speed) without fracture presumption.

Elastoplastic analysis of AA7075-O aluminum sheet by hybrid micro-scale representative volume element modeling with really-distributed particles and in-situ SEM experimental testing

• Presents a novel computationally-efficient reconstruction of 3D RVE model of second-phase particle-strengthened AA7075-O sheet with real distribution of particles based on FIB-SEM techniques. • Three types of second-phase particles (i.e., irregularly-shaped iron-rich particle Al 3 Fe, elliptically-shaped particle MgZn 2 , and needle-like particle CuAl 2 ) are determined using SEM-based EDS and EBSD techniques. • Presents a systematic study of the overall elastic-plastic response by developing and applying a hybrid experimental analysis and computational modeling framework. • Good agreement is observed in the comparison of RVE results with that of in-situ SEM tensile tests, indicating that the real 3D microstructure-based RVE models can accurately predict the plastic deformation and interfacial failure evolution in AA7075-O sheet. This paper addresses the challenge of reconstructing randomly distributed second-phase particle-strengthened microstructure of AA7075-O aluminum sheet material for computational analysis. The particle characteristics in 3D space were obtained from focused ion beam and scanning electron microscopy (FIB-SEM) and SEM-based Electron Backscatter Diffraction/Energy Dispersive X-ray Spectrometry (EBSD/EDS) techniques. A theoretical framework for analysis of elastic-plastic deformation of such 3D microstructures is developed. Slip-induced shear band formation, void initiation, growth and linkage at large plastic strains during uniaxial tensile loading were investigated based on reconstructed 3D representative volume element (RVE) models with real-distribution of particles and the results compared with experimental observations. In-situ SEM interrupted tension tests along transverse direction (TD) and rolling direction (RD), employing microscopic-digital image correlation (μ-DIC) technique, were carried out to investigate slip bands, micro-voids formation and obtain microstructural strain maps. The resulting local strain maps were analyzed in relation to the experimentally observed plastic flow localization, failure modes and local stress maps from simulations of RVE models. The influences of particle size, shape, orientation, volume fraction as well as matrix-particle interface properties on local plastic deformation, global stress-strain/strain-hardening curves and interfacial failure mechanisms were studied based on 3D RVE models. When possible, the model results were compared with in-situ tensile test data. In general, good agreement was observed, indicating that the real 3D microstructure-based RVE models can accurately predict the plastic deformation and interfacial failure evolution in AA7075-O aluminum sheet.

A Gradient-Enhanced Plasticity Based Phase-Field Model for Ductile Fracture Simulations

Ductile fracture is modeled by using a novel phase-field method of geometric type to avoid the use of the complicated discretization approaches for crack discontinuities. The plasticity model is defined by an over-nonlocal implicit gradient-enhanced framework, which is equivalent to the integral-type plasticity models and therefore strongly nonlocal. A modified phenomenological barrier function is used as the crack phase-field driving force by mainly considering the effects of the nonlocal plastic deformation under shear-dominated stress states. The ductile damage is assumed to solely affect the plastic energy stored capacity from the micro-mechanical perspective such that the proposed approach can be easily extended to more general loading conditions. The implementation of the proposed phase-field method is shown to be easily integrated into the commercial codes (e.g., ABAQUS) through the coupling use of several user interfaces. We present simulations of the shear band formation under axial compression and the ductile crack propagations in a single-edged notched plate, a slanted fracture specimen and a pure shear test specimen to elucidate the viability of the current nonlocal method. The numerical results adequately demonstrate that mesh dependency can be apparently alleviated if material softening occurs.

Dynamic response and adiabatic shear behavior of β-type Ti–Mo alloys with different deformation modes

This study examined the dynamic compressive properties and adiabatic shear behavior of β-type Ti–10Mo, Ti–15Mo, and Ti–22.5Mo alloys whose deformation modes are stress-induced α''-martensitic transformation combined with {332}<113> twinning, {332}<113> twinning, and dislocation slip under quasi-static loading, respectively. Based on the characterization of deformation microstructures, the deformation modes did not undergo significant change regardless of quasi-static and dynamic conditions. Their yield strength increased remarkably when the strain rate rose from 10−3 s−1 to 103 s−1, thus exhibiting the strain rate strengthening effect. The impact absorbed energy showed an increasing trend with a rise in strain rate, and the highest value (319.2 J/cm3) was observed in the Ti–15Mo alloy at a strain rate of 3956 s−1. The {332}<113> twinning deformation led to a high capacity for strain hardening, which delayed the formation of adiabatic shear bands, comprising the ultra-fine β-matrix and nano-scale ω-phase. Moreover, the deformed twins provided a tortuous and bifurcated path to enhance the propagation resistance of adiabatic shear bands, thereby further consuming the impact energy.

Microscopic mechanism of nanoscale shear bands in an energetic molecular crystal (α-RDX): A first-order structural phase transition

Nanoscale shear bands formed in many energetic molecular crystals upon shock compression [including 1,3,5-trinitro-$s$-triazine (RDX)] are considered as a defect-free mechanism for formation and growth of hot spots which control detonation initiation. Using classical molecular dynamics, we predict the formation of similar nanoscale shear bands in the \ensuremath{\alpha}-RDX crystal subjected to quasistatic isothermal uniaxial compression indicating a common mechanism of shear strain localization under both shock and quasistatic conditions. In the framework of the Ginzburg-Landau phenomenology coupled with the coarse-grained (CG) Helmholtz free energy of the crystal from first principles, we explore the thermodynamics of stress-induced lattice transformations under quasistatic uniaxial load. We show that the shear banding exhibits a critical behavior associated with a first-order structural phase transition with bands of localized twinning strain as transient microstructure. Analysis of the CG Helmholtz free energy suggests that the stress-induced core softening of the effective intermolecular interaction is a fundamental mechanism for a structural phase transition leading to the nanoscale shear bands.

Martensite stabilization in bulk metallic glass composites with shape memory crystals

The stress-induced martensitic transformation in “martensitic” or “shape memory” bulk metallic glass composites (BMGCs) plays a pivotal role in enhancing their plasticity and work-hardening capability. However, limited attention has been paid to the martensite stabilization in such BMGCs. This work investigated the effect of deformation and annealing on the reversibility of the martensitic transformation in shape memory BMGCs using experiments and simulations. It is found that the martensitic transformation from B2 to B19 ´ during mechanical loading becomes progressively more irreversible with increasing the strain. A large contribution to this effect can be ascribe to the stress field induced by the shear band formation, in accordance with the finite element simulation showing that residual stresses in the composites suppress the reverse transformation after deformation. Annealing the deformed composites above the glass transition temperature (Tg) relaxes the residual stresses, and the phase transformation becomes again fully recoverable. These results may have important implications for controlling the microstructure and mechanical properties of the shape memory BMGCs during thermomechanical treatments.

Microstructure evolution and shear band formation in an ultrafine-grained Ti–6Al–4V alloy during cold compression

It is generally accepted that dynamic recrystallization (DRX) is the result of shear banding in metallic materials. However, we observed the microstructure evolution in an ultrafine-grained Ti–6Al–4V alloy under quasi-static compression and found the formation of DRX induced micro shear bands at the initial stage of plastic deformation. It is of interest that the strain-localized regions experienced a two-step recrystallization process, thus resulting in the formation of refined dynamic recrystallized (DRX) grains in transition zones and nanograins in core regions of micro shear bands successively. It is suggested that the DRX taking place at local regions led to the strain softening, which subsequently accelerated the formation of micro shear bands. Micro shear bands nucleated, grew wider, multiplied and propagated by means of gradually consuming the DRX regions with the increase of local strains. Those micro shear bands are considered to contribute to synergetic plastic deformation in addition to dislocation slipping at lower strains, while some macro shear bands are regarded as the precursor of fracture at higher strains. Based on the observation results a new DRX mechanism of shear band was proposed. The experimental results in the present work can provide new evidences and novel insights of the shear-band formation, plastic deformation as well as failure mode in UFG alloys under quasi-static loading conditions.

Deformation behavior of crystalline/amorphous Al-Si nanocomposites with nanolaminate or nanofibrous microstructures

Deformation mechanisms in sputter-deposited crystalline Al/amorphous Si nanocomposites with nanolaminate or nanofibrous morphology are characterized by nanoindentation, micropillar compression testing and transmission electron microscopy (TEM). The nanofibrous composite having crystalline Al nanofibers with \ensuremath{\sim}40--50 nm in length and 15--20 nm in diameter embedded in amorphous Si exhibits strain hardening to a maximum flow stress of 2.9 GPa and no shear band (SB) formation in compression up to plastic strain exceeding 24%. On the other hand, nanolaminate composite that is composed of 80 nm crystalline Al layers and 20 nm amorphous Si layers exhibits catastrophic SBs starting at plastic strains in the range of 5--10%. Cross-sectional TEM of the deformed samples reveals a high density of stacking faults and twin boundaries in Al nanofibers and no microshear bands in the nanofibrous composite, suggesting plastic deformation in amorphous Si phase and crystalline Al nanofibers. Molecular dynamics simulations revealed that the plastic deformation in amorphous Si phase in the cosputtered films could be favored by the decrease in flow strength of amorphous Si with increasing Al solute concentration trapped in Si.