Fatigue behavior of polycrystalline thin copper films

Kraft, O.; Wellner, P.; Hommel, M.; Schwaiger, Ruth; Arzt, Eduard

doi:10.3139/146.020392

Cited by 78 publications

(51 citation statements)

References 21 publications

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“…A reduced diffusion length to the vacancy sink sites due to a smaller film thickness or a finer grain size is responsible for the increased fatigue life [31]. In other words, as the film thickness or grain size is reduced, the fatigue life at a constant applied total strain is increased [15,32,33]. This effect results from the fact that the voids formed by vacancy condensation are favorable sites for the generation of fatigue cracks [15].…”

Section: Fatigue Damage Formation and Annihilation In Metallic Bulk Amentioning

confidence: 92%

Effects of bending fatigue on the electrical resistance in metallic films on flexible substrates

Lee

et al. 2010

Met. Mater. Int.

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The increase of electrical resistance during the strain-controlled bending fatigue of 2 µm-thick inkjet-printed or vacuum deposited metallic films (Cu, Ag) on flexible substrates (BT: Bismaleimide Triazine, PI: Polyimide) was investigated. Electrical resistance increased with an increase in the number of fatigue cycles. The rate of increase in the electrical resistance of inkjet-printed Cu films was lower than that of thermally evaporated films. This phenomenon is attributable to the porous microstructure of inkjet-printed Cu films. The porous structure contains a lot of free volume and a large area of free surface, which can be a sinking site for vacancies formed during the cyclic deformation. It was confirmed that a smaller grain size leads to a lower rate of increase in the electrical resistance, which was ascribed to the easy vacancy annihilation due to a short diffusion length of the vacancy to the grain boundary which is a vacancy sinking site. The rate of increase in the electrical resistance was also influenced by the grain boundary geometry. The lower rate of the evaporated Ag film on a BT substrate was attributed to the crack-like grain boundaries, which were expected to behave like pores.

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Section: Fatigue Damage Formation and Annihilation In Metallic Bulk Amentioning

confidence: 92%

Effects of bending fatigue on the electrical resistance in metallic films on flexible substrates

Lee

et al. 2010

Met. Mater. Int.

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“…7. Although there are almost no reports on fatigue properties of bulk polycrystalline gold, the comparison of the nc gold films to bulk polycrystalline copper 47 , micron-thick copper films 48,49 and submicron-thick copper films on polyimide substrates 48,49 demonstrates that the nc gold films is of much The mutual misorientation angles among the corresponding areas in Fig. 3d.…”

Section: Discussionmentioning

confidence: 99%

Nanotwin-assisted grain growth in nanocrystalline gold films under cyclic loading

2014

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Under mechanical loading, nanocrystalline metals show unique behaviour, among the most common of which are high strength, mechanically induced grain growth and twin formation. However, mechanically induced grain growth is seldom correlated with twins. Here we report a clear relationship between grain growth and nanoscale twins in 20-nm-thick gold films with a grain size of B19 nm under cyclic loading based on atomic-scale observations and analyses. We find that the formation of nanotwins is an effective way to assist grain coarsening, following a fundamental process that the mutual formation of nanotwins in two neighbouring grains changes the local grain orientation and dissociates the grain boundary into new segments, which become more mobile. The proposed mechanism of nanotwin-assisted grain growth may have important implications for understanding the interface-mediated mechanisms of cyclic plastic deformation and for the interface engineering design of nanostructured metals with both high strength and good fatigue resistance.

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“…The failure mechanisms that give rise to a starter crack and then to its propagation are, on the other hand, different than under static conditions. Schwaiger, Kraft and co-workers [323][324][325][326][327] have shown that in Ag and Cu films, surface extrusions and voids at the coating/substrate interface dominate the fatigue life. Once again, the decohesion from the substrate during here cyclic deformation, leads to freestanding sections, which are more prone to localized plasticity and extrusion mechanisms, as recently confirmed on Ag films [328].…”

Section: Fracture and Fatigue Mechanismsmentioning

confidence: 97%

Failure of metals III: Fracture and fatigue of nanostructured metallic materials

2016

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a b s t r a c tPushing the internal or external dimensions of metallic alloys down to the nanometer scale gives rise to strong materials, though most often at the expense of a low ductility and a low resistance to cracking, with negative impact on the transfer to engineering applications. These characteristics are observed, with some exceptions, in bulk ultra-fine grained and nanocrystalline metals, nano-twinned metals, thin metallic coatings on substrates and freestanding thin metallic films and nanowires. This overview encompasses all these systems to reveal commonalities in the origins of the lack of ductility and fracture resistance, in factors governing fatigue resistance, and in ways to improve properties. After surveying the various processing methods and key deformation mechanisms, we systematically address the current state of the art in terms of plastic localization, damage, static and fatigue cracking, for three classes of systems: (1) bulk ultra-fine grained and nanocrystalline metals, (2) thin metallic films on substrates, and (3) 1D and 2D freestanding micro and nanoscale systems. In doing so, we aim to favour cross-fertilization between progress made in the fields of mechanics of thin films, nanomechanics, fundamental researches in bulk nanocrystalline metals and metallurgy to impart enhanced resistance to fracture and fatigue in high-strength nanostructured systems. This involves exploiting intrinsic mechanisms, e.g. to enhance hardening and rate-sensitivity so as to delay necking, or improve grain-boundary cohesion to resist intergranular cracks or voids. Extrinsic methods can also be utilized such as by hybridizing the metal with another material to delocalize the deformation -as practiced in stretchable electronics. Fatigue crack initiation is in principle improved by a fine structure, but at the expense of larger fatigue crack growth rates. Extrinsic toughening through hybridization allows arresting or bridging cracks. The content and discussions are based on experimental, theoretical and simulation results from the recent literature, and focus is laid on linking microstructure and physical mechanisms to the overall mechanical behavior.

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Fatigue behavior of polycrystalline thin copper films

Cited by 78 publications

References 21 publications

Effects of bending fatigue on the electrical resistance in metallic films on flexible substrates

Effects of bending fatigue on the electrical resistance in metallic films on flexible substrates

Nanotwin-assisted grain growth in nanocrystalline gold films under cyclic loading

Failure of metals III: Fracture and fatigue of nanostructured metallic materials

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