Prevalence of shear banding in compression of Zr41Ti14Cu12.5Ni10Be22.5 pillars as small as 150 nm in diameter

Wu, Xiaolei; Guo, Yuan‐ji; Wei, Q.; Wang, W.H.

doi:10.1016/j.actamat.2009.04.013

Cited by 68 publications

(42 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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].…”

mentioning

confidence: 99%

Dominant shear bands observed in amorphous ZrCuAl nanowires under simulated compression

2012

View full text Add to dashboard Cite

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...

show abstract

mentioning

confidence: 99%

Dominant shear bands observed in amorphous ZrCuAl nanowires under simulated compression

2012

View full text Add to dashboard Cite

show abstract

“…2,4,5 In addition to the atomic structure of the sample, shear band formation may also be influenced by extrinsic factors such as loading conditions, 6 microstructures 7 and the sample size. [8][9][10][11][12][13][14][15][16] Particularly, the size-dependent plasticity in MG systems has attracted considerable attention due to the advancement in micromechanical testing and sample preparation using focused-ion beam technique. Two related sizedependent plasticity have been investigated.…”

mentioning

confidence: 99%

Size-independent shear band formation in amorphous nanowires made from simulated casting

Shi

2010

Applied Physics Letters

View full text Add to dashboard Cite

Molecular dynamics simulations indicate that surfaces strongly influence the strain localization behavior of amorphous nanowires in tension. A sample preparation routine that simulates casting was employed to facilitate the relaxation of the sample surface. Samples as short as 15 nm (7.5 nm in diameter)form dominant shear bands during deformation. The elastic energy release during plastic deformation is sufficient to provide the excess potential energy required for the shear band nucleation at rather small sample sizes. The results show that shear band formation is almost size-independent and is bounded only by its own length scale.

show abstract

“…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.…”

mentioning

confidence: 99%

“…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.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

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

Yang

et al. 2009

J. Mater. Res.

View full text Add to dashboard Cite

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...

show abstract

Prevalence of shear banding in compression of Zr41Ti14Cu12.5Ni10Be22.5 pillars as small as 150 nm in diameter

Cited by 68 publications

References 61 publications

Dominant shear bands observed in amorphous ZrCuAl nanowires under simulated compression

Dominant shear bands observed in amorphous ZrCuAl nanowires under simulated compression

Size-independent shear band formation in amorphous nanowires made from simulated casting

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

Contact Info

Product

Resources

About