Compression testing of metallic glass at small length scales: Effects on deformation mode and stability

Bharathula, Ashwini; Lee, Seok‐Woo; Wright, Wendelin J.; Flores, Katharine M.

doi:10.1016/j.actamat.2010.06.054

Cited by 103 publications

(56 citation statements)

References 34 publications

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“…Obviously, for pillars with smaller enough size, the Cu-Zr-Al MG exhibited very good plastic deformability. Similar phenomena were reported later in other works [10,22,[28][29][30][31][32] However, a close examination on these works is ready to find that all the tested samples had a tapered geometry which will undoubtedly generate stress/strain gradient with their magnitude determined by the taper angle and the initial top diameter. [45] Therefore, it had been argued that the observed plastic behavior of MGs during the compression tests might stem from the tapered sample geometry and the imperfect contact interface.…”

Section: Strength-size Relationshipmentioning

confidence: 67%

Mechanical Behavior of Micronanoscaled Metallic Glasses

Tian

Wang

Shan

2016

Materials Research Letters

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In this paper, research on the mechanical behavior of micronanoscaled metallic glasses (MGs) is reviewed, with an emphasis on works achieved through in situ transmission electron microscope. It was found that the strength of micronanoscaled MGs has a nonlinear dependence on sample size. Corresponding to the transition of size-dependent strength, the deformation mechanism of MGs changes gradually from brittle to ductile with the critical transition size being affected by strain rate, e-beam irradiation and thermal history of the sample. Besides monotonic loading, the mechanical behaviors of MGs in response to cyclic loadings and fatigue tests are also reviewed. Keywords: Metallic Glasses, Micronanoscaled, Plasticity, Strength, Cyclic LoadingIntroduction Metallic glasses (MGs), also known as amorphous metals, are materials composed of metal components but without crystalline structure.[1-3] The lack of long-range order, that is, atoms do not register in periodic lattice sites, renders MGs unique in mechanical behaviors. [4][5][6][7] Unlike crystalline metals, MGs do not have dislocation or deformation twinning as plastic carriers. When the applied mechanical load exceeds their yield strength, bulk MGs usually deform through the formation of shear band, a thin band where large shear strains localized [8], usually in a catastrophic manner. The stress level required for the nucleation and propagation of shear band is much higher than that for dislocations or twins in bulk crystalline materials, usually on the GPa level. Without early yielding, the measured elastic limit for bulk MGs can be up to 2% [4,9], much larger than their crystalline counterparts. Even though the brittleness and high cost limit the commercialization of bulk MGs, recent studies [10][11][12] demonstrated that micronanoscaled (refer to samples with their size ranged from 10 nm to 10 μm [13]) MGs own outstanding strength and reasonable plastic deformability which make them attractive for applications in Micro/Nano electro-mechanical systems (M/NEMS). Consequently, a systematic study of the mechanical properties of

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Section: Strength-size Relationshipmentioning

confidence: 67%

Mechanical Behavior of Micronanoscaled Metallic Glasses

Tian

Wang

Shan

2016

Materials Research Letters

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“…Both size-dependent [3,[7][8][9][10] and size-independent [12][13][14] shear banding behaviors in MG nanorods have been reported in experiments. Moreover, MD simulations on two-dimensional or threedimensional thin-slab geometry [15,16] show clear shear band formation, while MD simulations on three-dimensional nanowire samples show homogeneous flow [17,18].…”

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confidence: 99%

Dominant shear bands observed in amorphous ZrCuAl nanowires under simulated compression

2012

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We observed the formation of dominant shear bands in model ZrCuAl metallic glass (MG) nanowires (18-nm-long) in molecular dynamics simulations, which implies size-independent incipient plasticity in MG materials. The MG nanowires were prepared using the simulated casting technique to ensure proper relaxation of sample surfaces. Under uniaxial compression, shear bands initiate at the surfaces and lead to reduced icosahedral short-range order. The shear band formation is sensitive to sample thermal-history, which calls for careful consideration of sample preparation effects in both experimental and numerical studies of sizeeffect in MG samples.Metallic glasses (MG), unlike other forms of glasses, have distinctive mechanical properties including large elastic strain limit and high tensile strength [1,2]. Metallic glasses, however, suffer from catastrophic failure upon free propagating shear bands. The formation of localized shear bands strongly compromises the practical usages of the metallic glasses for load-bearing applications. One promising way to overcome this shortcoming of metallic glasses is to reduce the sample size of MGs using Focused Ion Beam (FIB) [3] or hot extension [4]. It has been shown that MG in the form of nanowires can exhibit large tensile strain [5,6]. This is thought to be due to the limited spatial scale of nanowires which is insufficient for shear band propagation and maturation into runaway cracks [1].Although shear band propagation and maturation into cracks are likely size-dependent [1], it is still not clear whether the initiation of shear bands (incipient plasticity) is size-dependent. Both size-dependent [3,7-10] and size-independent [12-14] shear banding behaviors in MG nanorods have been reported in experiments. Moreover, MD simulations on two-dimensional or threedimensional thin-slab geometry [15,16] show clear shear band formation, while MD simulations on three-dimensional nanowire samples show homogeneous flow [17,18]. Recently, Shi [11] proposed a new numerical sample preparation procedure termed "simulated casting", during which a molten liquid confined in a cylindrical container is quenched directly into a glassy nanowire. This sample preparation technique is advantageous in comparison to the conventional cut-form-bulk procedure to obtain nanowire samples in computer simulation. Surfaces resulting from the traditional cut-from-bulk procedure are usually not sufficiently relaxed at the processing temperature, whereas in the simulated casting technique, surfaces are created from the melt directly and atoms on the surfaces are fully relaxed. For MG nanowires obtained from the cut-frombulk procedure, homogeneous deformation followed by necking was observed owing to unrelaxed surfaces [11]. By contrast, it was shown that MG nanowires obtained from the simulated casting, thus with relaxed surfaces, exhibit shear banding with a sample length longer than 13 nm, as a result of competition between elastic energy and shear band energy [11]. Interestingly, this critical length va...

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“…In this respect micro-pillars compression is a new technique which has been widely investigated during the last six years to measure the mechanical properties of materials at the micron and submicron scale. Recently micropillar compression has been extensively used for the investigation of size effects in metals [15,16,17] and also metallic glasses [18,19].…”

Section: Introductionmentioning

confidence: 99%

Micropillar Testing of Amorphous Silica

Lacroix

Chomienne

Kermouche

et al. 2012

Int J of Appl Glass Sci

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Amorphous silica exhibits a complex mechanical response. The elastic regime is highly non linear while plastic flow does not conserve volume, resulting in densification. As a result the quantification of a reliable constitutive equation is a difficult task. We have assessed the potential of micro-pillar compression testing for the investigation of the micromechanical properties of amorphous silica. We have calculated the response of amorphous silica micropillars as predicted by Finite Element Analysis. The results were compared to preliminary micro-compression tests. In the calculations an advanced constitutive law including plastic response, densification and strain hardening was * Email: remi.lacroix@saint-gobain.com. 1This is the pre-peer reviewed version of the following article: International Journal of Applied Glass Science 3 [1] 3643 (2012), which has been published in final form at http: //onlinelibrary.wiley.com/doi/10.1111/j.2041-1294.2011.00075.x/abstract used. Special attention was paid to the evaluation of the impact of substrate compliance, pillar misalignment and friction conditions. We find that amorphous silica is much more amenable than some metals to microcompression experiments due to a comparatively high ratio between yield stress and elastic modulus. The simulations are found to be very consistent with the experimental results. However full agreement cannot be obtained without allowance for the non linear response of amorphous silica in the elastic regime.

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Compression testing of metallic glass at small length scales: Effects on deformation mode and stability

Cited by 103 publications

References 34 publications

Mechanical Behavior of Micronanoscaled Metallic Glasses

Mechanical Behavior of Micronanoscaled Metallic Glasses

Dominant shear bands observed in amorphous ZrCuAl nanowires under simulated compression

Micropillar Testing of Amorphous Silica

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