Shear‐Band Dynamics in Metallic Glasses

Maaß, R.; Löffler, Jörg F.

doi:10.1002/adfm.201404223

Cited by 211 publications

(93 citation statements)

References 96 publications

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“…Another aspect is the influence of nanocrystallization on the shear band dynamics. Since the plasticity of metallic glasses is thermally activated, a high applied strain rate may decrease the viscosity of the shear band [32]. This trend is observed for the MS10 samples, as shown in Fig.…”

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confidence: 51%

Structure and dynamics of shear bands in amorphous–crystalline nanolaminates

et al. 2016

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a b s t r a c tThe velocities of shear bands in amorphous CuZr/crystalline Cu nanolaminates were quantified as a function of strain rate and crystalline volume fraction. A rate-dependent transition in flow response was found in a 100 nm CuZr/10 nm Cu nanolaminates. When increasing the Cu layer thickness from 10 nm to 100 nm, the instantaneous velocity of the shear band in these nanolaminates decreases from 11.2 lm/s to <$500 nm/s. Atom probe tomography and transmission election microcopy observation revealed that in post-deformed pillars both grain rotation in the crystalline portion and non-diffusive crystallization in the amorphous layer affect the viscosity of shear bands.At room temperature, the plasticity of metallic glasses (MGs) is mainly achieved by the initiation and propagation of nanometer sized shear bands [1]. Establishing a fundamental understanding of these shear bands and controlling them for avoiding catastrophic propagation are particularly urgent before rendering MGs into the class of advanced structural/functional materials. Therefore, multiple studies have addressed the structural [2], chemical [3] and dynamic properties [4] of shear bands. Shear bands are also considered to be possible sites for nanocrystallization in systems such as Al-based [5] and Zr-based metallic glasses [6]. The strain induced devitrification process has been observed in nanoindentation [7], uniaxial compression [8] and cold rolling [9] of metallic glasses. However, it is still unclear whether nucleation of crystalline phases is driven by adiabatic heating [10] or by the increase of free volume [11]. The role of these crystalline phases in influencing the shear band propagation is also unknown owing to the lack of structural and chemical information about shear bands.At least the introduction of known crystalline phases into an amorphous matrix promises an enhanced plasticity [12] by forming multiple shear bands or a dislocation/shear mediated co-deformation process [13]. The morphology of the shear bands is highly dependent on the crystalline phase fraction, by which the shear band dynamics is highly influenced. Some pioneering studies on pure metallic glasses reveal that a single shear band can propagate 0.3-14 lm within a millisecond [14,15], but little work was done for the metallic glass/crystalline nanocomposite structures.In this study, a quantitative assessment of the shear band dynamics in 100 nm amorphous CuZr/x nm crystalline Cu (x = 10, 50, 100 nm) nanolaminates within a time interval of 10 À2 ms was carried out. Transmission Electron Microscopy (TEM) and Atom Probe Tomography (APT) were jointly used for evaluating additional structural and chemical features of shear bands after deformation.Amorphous CuZr/crystalline Cu nanolaminates were deposited on Si (1 0 0) wafers by direct current magnetron sputtering. For these nanolaminates, the thickness of the individual amorphous CuZr layers were fixed to 100 nm, while the thickness of the nanocrystalline Cu layers varied between 10, 50 and 100 nm. Accordingly, t...

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confidence: 51%

Structure and dynamics of shear bands in amorphous–crystalline nanolaminates

et al. 2016

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“…Similar scaling analyses were used in single crystalline Ni [56] and LiF [57] micro-pillars, showing the values of α are 1.5 and 1.8-2.9, respectively. The observation of intermittent flow and power-law scaling (or scale-free behaviour) is comparable to those observed in metal [56] and metallic glasses [58] pillars, suggesting that the plastic flow for DQC pillars is controlled by a nucleation and propagation process, at least in the tested size and temperature regime.…”

Section: Serrated Flowssupporting

confidence: 67%

Bridging room-temperature and high-temperature plasticity in decagonal Al–Ni–Co quasicrystals by micro-thermomechanical testing

Zou

Wheeler

Sologubenko

et al. 2016

Philosophical Magazine

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(2016) Bridging room-temperature and high-temperature plasticity in decagonal Al-Ni-Co quasicrystals by micro-thermomechanical testing, Philosophical Magazine, 96:32-34, 3356-3378, DOI: 10.1080/14786435.2016 Ever since quasicrystals were first discovered, they have been found to possess many unusual and useful properties. A long-standing problem, however, significantly impedes their practical usage: steadystate plastic deformation has only been found at high temperatures or under confining hydrostatic pressures. At low and intermediate temperatures, they are very brittle, suffer from low ductility and formability and, consequently, their deformation mechanisms are still not clear. Here, we systematically study the deformation behaviour of decagonal Al-Ni-Co quasicrystals using a micro-thermomechanical technique over a range of temperatures (25-500 °C), strain rates and sample sizes accompanying microstructural analysis. We demonstrate three temperature regimes for the quasicrystal plasticity: at room temperature, cracking controls deformation; at 100-300 °C, dislocation activities control the plastic deformation exhibiting serrated flows and a constant flow stress; at 400-500 °C, diffusion enhances the plasticity showing homogenous deformation. The micrometersized quasicrystals exhibit both high strengths of ~2.5-3.5 GPa and enhanced ductility of over 15% strains between 100 and 500 °C. This study improves understanding of quasicrystal plasticity in their lowand intermediate-temperature regimes, which was poorly understood before, and sheds light on their applications as small-sized structural materials.

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“…bending [9][10][11][12], shearing [13], compression [14,15], or in fracture toughness measurements [16]. Deeper understanding of shear bands is therefore key to creating new design strategies for developing BMGs and BMG structures with improved mechanical properties, and motivates ongoing physical characterization of individual shear bands [17]. To this end, we have studied the dynamics of single shear bands under compression in the Zr-Cu-Al BMG system as a function of temperature and composition.…”

Section: Introductionmentioning

confidence: 99%