Indentation size effect and shear transformation zone size in a bulk metallic glass in two different structural states

Choi, In Chul; Zhao, Yakai; Kim, Yong Jae; Yoo, Byung Gil; Suh, Jin-Yoo; Ramamurty, Upadrasta; Jang, Jae-il

doi:10.1016/j.actamat.2012.08.061

Cited by 139 publications

(70 citation statements)

References 30 publications

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“…Pan et al also reported less dense atomic packing has larger STZ volume in a ZrCu-Ni-Al metallic glass [8]. However, it does not reach an agreement on the correlation between the free volume content and STZ volume that Jang et al reported a negative effect of free volume on STZ volume [27]. STZ is thought to be the plastic unit in metallic glass.…”

Section: Resultsmentioning

confidence: 87%

“…Based on Schuh's work [26], the activation volume of the nucleation events for the onset of the plasticity can be estimated through the statistical method, which relies on the cumulative distribution of the yield strength. Recently, Jang et al developed and applied such statistical method on metallic glass to estimate the STZ activation volume [27]. The cumulative probability of the thermally-assisted and stress-biased τ m can be described as the red fitting lines in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Nanoindentation investigation on the creep mechanism in metallic glassy films

Peng

Feng

et al. 2016

Materials Science and Engineering: A

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a b s t r a c tUsing the magnetron sputtering technique, two metallic glassy films namely Cu 44.3 Zr 45.1 Al 10.6 and Cu 44.2 Zr 43 Al 11.3 Ti 1.5 were prepared by alloy targets. The minor Ti addition effectively induces excess free volume. Upon spherical nanoindentation, the creep behaviors of both films were studied at various peak loads. As the increase of peak load, the creep deformations became more severely in both samples. Interestingly, Cu-Zr-Al-Ti film crept stronger than Cu-Zr-Al at small-load holdings (nominal elastic regimes), whereas it is opposite at high-load holdings (plastic regimes). The creep characteristic could be intrinsically related to the scale variation of the shear transformation zone (STZ) with Ti addition. Statistical analysis was employed to estimate the STZ volume, which increased by 60% with Ti addition in the Cu-Zr-Al film. The finite element modeling indicated that STZs would be activated even at the minimum load we adopted. Higher activation energy of larger STZs in Cu-Zr-Al-Ti enables less flow units, which offsets the creep enhancement by the excess free volume with Ti addition. The deeper the pressed depth of the indenter, the more contribution of the STZ operation on creep deformation. In addition, experimental observation on the creep flow rates implies that STZ could be the dominating mechanism at the steady-state creep. This study reveals that STZ volume could also be important to the time-dependent plastic deformation in metallic glass, besides as a key parameter for instantaneous plasticity.

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Section: Resultsmentioning

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Nanoindentation investigation on the creep mechanism in metallic glassy films

Peng

Feng

et al. 2016

Materials Science and Engineering: A

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“…28,35,36 For indentation with a Berkovich tip, the load P can be expressed in terms of the effective elastic modulus E eff and elastic displacement h as…”

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confidence: 99%

Fracture-resistant thin-film metallic glass: Ultra-high plasticity at room temperature

Lee

Chu

et al. 2016

APL Materials

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We report the first example of room-temperature rubber-like deformation in thin-film metallic glasses (TFMGs), 260-nm-thick Zr60Cu24Al11Ni5 layers, under ultra-high shear strain. The TFMGs were deposited, with no external heating, on Zr-based bulk metallic glass (BMG) and Si(001) substrates by rf magnetron sputtering in a 3 mTorr Ar plasma. Cross-sectional transmission electron microscopy (XTEM) analyses and nanoindentation results reveal that the TFMGs undergo an incredibly large shear strain, estimated to be ∼4000%, during fatigue tests, and thickness reductions of up to 61.5%, with no shear-banding or cracking, during extreme nanoindentation experiments extending through the film and into the substrate. TFMG/BMG samples also exhibit film/substrate diffusion bonding during deformation as shown by high-resolution XTEM.

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“…The load, P 1 , at which the first pop-in is noted for each P À h curve and was utilized to compute the mean contact pressure, P m ¼ [17]. Note that this procedure is [10,11]. Variations in the average values of E and P m for the four different TFMGs are plotted in Fig.…”

Section: Shear Yield Strain Of Various Tfmgsmentioning

confidence: 99%