The mechanisms of indentation creep

Li, W.B.; Henshall, J. L.; Hooper, Robert; Easterling, K. E.

doi:10.1016/0956-7151(91)90043-z

Cited by 233 publications

(111 citation statements)

References 9 publications

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“…In crystalline alloys, the time-dependent plastic deformation in nanoindentation could be ascribed to various mechanisms such as dislocation glide (or climb), twins deformation, lattice diffusion and boundary diffusion et al [22]. For metallic glasses, the free volume evolution [14] and interfacial diffusion [23] were expected to be the deformation modes of creep flow within elastic and/or shallow depth regime.…”

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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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: 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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“…The data from pyramidal indentation creep is therefore always a mixture of the different creep stages, depending on the localized stress and strain states. However, nanoindentation creep data are commonly analyzed making the assumption of steady-state creep, 41 which is a good approximation that greatly simplifies the analysis. Indeed, the steady-state creep-rate is strongly dependent on the applied stress and can be well described by the simplified expression:…”

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confidence: 99%

An improved long-term nanoindentation creep testing approach for studying the local deformation processes in nanocrystalline metals at room and elevated temperatures

et al. 2013

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The strain-rate sensitivity of ultrafine-grained aluminum (Al) and nanocrystalline nickel (Ni) is studied with an improved nanoindentation creep method. Using the dynamic contact stiffness thermal drift influences can be minimized and reliable creep data can be obtained from nanoindentation creep experiments even at enhanced temperatures and up to 10 h. For face-centered cubic (fcc) metals it was found that the creep behavior is strongly influenced by the microstructure, as nanocrystalline (nc) as well as ultrafine-grained (ufg) samples show lower stress exponents when compared with their coarse-grained (cg) counterparts. The indentation creep behavior resembles a power-law behavior with stress exponents n being ; 20 at room temperature. For higher temperatures the stress exponents of ufg-Al and nc-Ni decrease down to n ; 5. These locally determined stress exponents are similar to the macroscopic exponents, indicating that similar deformation mechanisms are acting during indentation and macroscopic deformation. Grain boundary sliding found around the residual indentations is related to the motion of unconstrained surface grains.

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“…Note that significant creep occurs at room temperature. Nanoindenter experiments conducted by Li et al (1991) exhibited significant creep only at high temperatures (greater than or equal to 0.25 times the melting point of silicon). The mechanism of dislocation glide plasticity is believed to dominate the indentation creep process on the macroscale.…”

Section: Indentationmentioning

confidence: 99%

Nanotribology, nanomechanics and nanomaterials characterization

Bhushan

2007

Phil. Trans. R. Soc. A.

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Nanotribology and nanomechanics studies are needed to develop fundamental understanding of interfacial phenomena on a small scale and to study interfacial phenomena in magnetic storage devices, nanotechnology and other applications. Friction and wear of lightly loaded micro/nanocomponents are highly dependent on the surface interactions (a few atomic layers). These structures are generally coated with molecularly thin films. Nanotribology and nanomechanics studies are also valuable in the fundamental understanding of interfacial phenomena in macrostructures and provide a bridge between science and engineering. An atomic force microscope (AFM) tip is used to simulate a single-asperity contact with a solid or lubricated surface. AFMs are used to study the various tribological phenomena that include surface roughness, adhesion, friction, scratching, wear and boundary lubrication. In situ surface characterization of local deformation of materials and thin coatings can be carried out using a tensile stage inside an AFM. Mechanical properties such as hardness, Young's modulus of elasticity and creep/relaxation behaviour can be determined on micro-to picoscales using a depth-sensing indentation system in an AFM.

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The mechanisms of indentation creep

Cited by 233 publications

References 9 publications

Nanoindentation investigation on the creep mechanism in metallic glassy films

Nanoindentation investigation on the creep mechanism in metallic glassy films

An improved long-term nanoindentation creep testing approach for studying the local deformation processes in nanocrystalline metals at room and elevated temperatures

Nanotribology, nanomechanics and nanomaterials characterization

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