Extraction of bulk metallic-glass yield strengths using tapered micropillars in micro-compression experiments

Ye, J.C.; J, Lu; Yang, Yong; Liaw, Peter K.

doi:10.1016/j.intermet.2009.08.011

Cited by 55 publications

(23 citation statements)

References 31 publications

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“…7(b), the data of r y vs. E obtained for the TFMGs are plotted together with those of the BMGs, from which it can be seen that all experimental data seemingly collapse onto the same master curve of r y ¼ E/50. As H is known to be 2.8-3 times r y for a variety of MGs, 19 the current finding strongly implies that the previous film softening, as revealed by the nanoindentation experiments, should stem from a tensile residual stress in the TFMGs, which facilitates yielding in the TFMGs bonded to a Si substrate, but is released after FIB milling and plays no role in microcompression. …”

Section: -3supporting

confidence: 55%

“…To highlight this, the hardness-versusmodulus data obtained from different types of Zr-based TFMGs were plotted on the same graph with those of BMGs. 18,19 As analogous to the known relation between the strength (r y ) and Young' modulus (E) of BMGs, 20 i.e., r y ¼ 0.02E, the hardness vs. modulus data can be also fitted quite well to an empirical relation, i.e., H ¼ 0.069E, across a wide range of modulus. As shown in Fig.…”

Section: -2mentioning

confidence: 70%

“…In principle, one can select either the Mohr-Coulomb (MC) or Drucker-Prager (DP) model to estimate r r , both of which have been widely accepted as the yielding criterion for MGs in the MG literature. 19,[22][23][24] Here, both two are utilized for the sake of comparison. After the necessary derivations, one can readily obtain the following formulas:…”

Section: A Residual Stressmentioning

confidence: 99%

“…where h is the shear angle ($42 ) in a MG sample under compression, l is the so-called frictional coefficient ($0.1 for Zr-based MGs), 19 and f is the parameter in the DP model accounting for the tension-compression asymmetry, which can be expressed as f ¼ 3 r c Àr t r c þr t and usually takes on the value $0.13 for the Zr-based MGs. Here r c and r t denote the compressive and tensile yield strength of a MG, respectively.…”

Section: A Residual Stressmentioning

confidence: 99%

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Hardness, yield strength, and plastic flow in thin film metallic-glass

Chu

Chen

et al. 2012

Journal of Applied Physics

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Lithiation-induced tensile stress and surface cracking in silicon thin film anode for rechargeable lithium battery J. Appl. Phys. 112, 093507 (2012) Mechanical and thermal behaviors of nitrogen-doped Zr-Cu-Al-Ag-Ta--An alternative class of thin film metallic glass Appl. Phys. Lett. 101, 181902 (2012) Effect of relative humidity on crack propagation in barrier films for flexible electronics J. Appl. Phys. 112, 083520 (2012) Torsion fracture of carbon nanocoils J. Appl. Phys. 112, 084311 (2012) Additional information on J. Appl. Phys. Thin film metallic-glasses (TFMGs) are a promising structural material for fabricating the next generation of micro-and nano-devices; however, a comprehensive study is still lacking today for understanding their mechanical behaviors. In this article, we present a systematic study on the Zr 53 Cu 29 Al 12 Ni 6 TFMGs with varying thicknesses. Other than the intrinsic factor of structural amorphousness, our study pinpoints other extrinsic variables that could affect the hardness and yield strength of the TFMGs. Furthermore, the experimental results from microcompression show that the plastic flow in the TFMG-based micropillars exhibit strong sample size-and-shape dependence, which manifests as a smooth plastic deformation transition from the inhomogeneous to homogeneous mode when the TFMG-based micropillars with a submicron-scale film thickness are deformed into the shape of a low aspect ratio. V C 2012 American Institute of Physics.

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Section: -3supporting

confidence: 55%

Section: -2mentioning

confidence: 70%

Section: A Residual Stressmentioning

confidence: 99%

Section: A Residual Stressmentioning

confidence: 99%

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Hardness, yield strength, and plastic flow in thin film metallic-glass

Chu

Chen

et al. 2012

Journal of Applied Physics

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“…Before proceeding, it should be noted that the micropillar tapering can help to stabilize the shear-banding process. Through the rigorous analysis, 11 it can be shown that, in the tapered micropillar geometry, the angle of the shear band relative to the loading axis deviates from that in the nontapered one. Such a deviation implies that shear band may be more stable running in a less favorable shear direction.…”

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confidence: 99%

Effects of sample geometry on deformation modes of bulk metallic glasses at the nano/micrometer scale

Yang

et al. 2009

J. Mater. Res.

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Intense debates have been prompted concerning whether homogeneous deformation can be achieved in bulk metallic glasses at room temperature through the suppression of shear bands at the submicron scale. In this short communication, we demonstrate that multiple shear banding can be successfully attained via a proper modification of the microsample geometry, resulting in the appearance of a homogeneous deformation mode at the submicron scale. However, the apparent deformation homogeneity in our microcompression experiment is a manifestation of the sample geometry effect on the propagation rather than nucleation of shear bands.Understanding the behavior of shear bands in bulk metallic glasses (BMGs) is critical in the design of a new class of BMGs with superior mechanical properties. In BMG bulk samples, shear bands tend to propagate in a catastrophic way, resulting in the subsequent brittlelike fracture, which renders the BMGs with limited ductility at room temperature.1 However, at the micrometer scale, shear bands were found to behave in a ductile manner, propagating without causing the sudden fracture of the microsample throughout a large plastic deformation process.2 Moreover, it was reported that shear bands could even be completely suppressed by reducing the sample size into the submicron scale, which led to a homogeneous deformation mode at room temperature. 3,4 However, the idea of the shear-band suppression is controversial and was later challenged by a few researchers based on their results of the microcompression experiments, [5][6][7] in which no homogeneous deformation mode was observed on the micropillars even though their diameters were reduced to a level less than that observed in the homogeneous deformation mode. It can be argued that the difference of the experimental results originates from the chemical composition of the microsamples, i.e., different BMGs have different critical length scales below which the shear bands cannot be nucleated. Thus, the homogeneous deformation is still an intrinsic effect, reflecting the shear-banding behavior at the small size scale. However, there is another extrinsic effect that could also cause the apparent deformation homogeneity, but was somehow ignored in previous studies, [2][3][4]6 which is derived from the sample geometry and the associated boundary conditions.In mechanical testing of single crystals, it is known that the grips play an important role in determining the deformation morphology of a tensile specimen. If the lateral translations of both grips are constrained, a dislocation single slip is not favored, and, thus, the resulting deformation morphology is a reflection of the combined effect of the sample geometry and dislocation dynamics. Likewise, although shear banding is essentially heterogeneous in BMGs, an apparent homogeneous deformation mode is still possible as long as the shear offset resulting from the propagation of the small shear band is insignificant in changing the structural integrity of the microsample. In such a case, the deforma...

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In situTransmission Electron Microscopy on Metals

Hosson¹

2012

Handbook of Nanoscopy

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Extraction of bulk metallic-glass yield strengths using tapered micropillars in micro-compression experiments

Cited by 55 publications

References 31 publications

Hardness, yield strength, and plastic flow in thin film metallic-glass

Hardness, yield strength, and plastic flow in thin film metallic-glass

Effects of sample geometry on deformation modes of bulk metallic glasses at the nano/micrometer scale

In situTransmission Electron Microscopy on Metals

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