Evolution of shear bands in bulk metallic glasses under dynamic loading

Zhang, Hongwen; Maiti, Spandan; Subhash, Ghatu

doi:10.1016/j.jmps.2008.01.008

Cited by 46 publications

(42 citation statements)

References 56 publications

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“…(2)) [18]. It is worth noting that the CSM deals only with the onset of (inhomogeneous) plastic yielding rather than the post-yielding behavior, namely, the shear-banding process, when BMGs are subjected to macroscopic strain rate _ c. In fact, recent works [40][41][42] have demonstrated that the local shear strain rates within the band can significantly exceed the applied strain rate.…”

Section: Discussionmentioning

confidence: 99%

Shear transformation zone volume determining ductile–brittle transition of bulk metallic glasses

et al. 2011

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Three-point bending experiments were performed on as-cast and annealed samples of Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 (Vit105) bulk metallic glasses over a wide range of temperatures varying from room temperature (293 K) to liquid nitrogen temperature (77 K). The results demonstrated that the free volume decrease due to annealing and/or cryogenic temperature can reduce the propensity for the formation of multiple shear bands and hence deteriorate plastic deformation ability. We clearly observed a sharp ductile-to-brittle transition (DBT), across which microscopic fracture feature transfers from micro-scale vein patterns to nano-scale periodic corrugations. Macroscopically, the corresponding fracture mode changes from ductile shear fracture to brittle tensile fracture. The shear transformation zone volume, taking into account free volume, temperature and strain rate, is proposed to quantitatively characterize the DBT behavior in fracture of metallic glasses.

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Section: Discussionmentioning

confidence: 99%

Shear transformation zone volume determining ductile–brittle transition of bulk metallic glasses

et al. 2011

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“…Regarding the strain-rate effect, Figure S4 shows the deformation morphologies of uniaxial compression tests with a low strain rate of 0.00001 ps -1 , which are very similar to Figure 2. It has been shown experimentally [25] that lower strain rates lead to larger shear band spacings (i.e., more localized deformation). Thus, shear banding is expected to be the main deformation mode for MG nanowires with very low quenching rate under very low strain rates.…”

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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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“…The free-volume diffusion determines the thickness of a shear band [26,27,33]. Thermal and momentum diffusions that are out of a shear band and into its neighbouring medium can produce a heat-affected zone [34,35] and a momentum diffusion zone or shear-band spacing [25,36,37], respectively.…”

Section: Introductionmentioning

confidence: 99%

“…For example, combining the momentum diffusion model firstly proposed by Grady and Kipp [31] with the free-volume and heat evolution, the evolution features of shear bands (e.g., shear-band toughness, thickness and spacing) [25,26,37,38] were investigated. In these studies, a rigideplastic assumption was applied and thus the influence of elastic strain energy on shear banding is disregarded.…”

Section: Introductionmentioning

confidence: 99%

“…In these studies, a rigideplastic assumption was applied and thus the influence of elastic strain energy on shear banding is disregarded. As is well known, however, shear banding in solids can be considered as a dissipation system [1,6,16,25,26,37,38], and elastic strain energy contributes to shear localization [39]. In particular, since the localized plastic flow in BMGs is concentrated in a rather thin shear band surrounded by an elastically deformed matrix, the elastic strain energy cannot be ignored.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic fragmentation induced by network-like shear bands in a Zr-based bulk metallic glass

et al. 2015

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Evolution of shear bands in bulk metallic glasses under dynamic loading

Cited by 46 publications

References 56 publications

Shear transformation zone volume determining ductile–brittle transition of bulk metallic glasses

Shear transformation zone volume determining ductile–brittle transition of bulk metallic glasses

Dominant shear bands observed in amorphous ZrCuAl nanowires under simulated compression

Dynamic fragmentation induced by network-like shear bands in a Zr-based bulk metallic glass

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