Mechanical Size‐Effects in Miniaturized and Bulk Materials

Dehm, Gerhard; Motz, Christian; Scheu, Christina; Clemens, Helmut; Mayrhofer, P.H.; Mitterer, Christian

doi:10.1002/adem.200600153

Cited by 68 publications

(33 citation statements)

References 86 publications

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“…The uniaxial compression methodology was first introduced by Uchic et al 5 Greer et al 56 extended this method to the nanoscale region; they observed that single crystalline Au NPs exhibited unprecedented strengths that were nearly 50 times greater than their bulk counterparts. More recently, the understanding of elasticity and plasticity in small volumes has been further enriched through tensile experiments performed by Mompioua et al, 32 Kiener et al 57 and Dehm et al 58 Because the deformation mechanism of these micro-NPs have been comprehensively reviewed by Zhu and Li, 10 Dehm, 15,39,58 Uchic et al 52 Kraft et al, 53 Legros et al 59 and Greer et al, 55 we only provide a brief summary here. Next, we focus on the atomic-scale in situ TEM investigations on NMs that are o100 nm.…”

Section: Direct Atomic Mechanisms Of the Size Effects On The Unusual mentioning

confidence: 99%

In situ experimental mechanics of nanomaterials at the atomic scale

2013

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Sub-micron and nanostructured materials exhibit high strength, ultra-large elasticity and unusual plastic deformation behaviors. These properties are important for their applications as building blocks for the fabrication of nano-and micro-devices as well as for their use as components for composite materials, high-strength structural and novel functional materials. These nano-related deformation and mechanical behaviors, which are derived from possible size and dimensional effects and the low density of defects, are considerably different from their conventional bulk counterparts. The atomic-scale understanding of the microstructural evolution process of nanomaterials when they are subjected to external stress is crucial for understanding these 'unusual' phenomena and is important for designing new materials, novel structures and applications. This review presents the recent developments in the methods, techniques, instrumentation and scientific progress for atomic-scale in situ deformation dynamics on nanomaterials, including nanowires, nanotubes, nanocrystals, nanofilms and polycrystalline nanomaterials. The unusual dislocation initiation, partial-full dislocation transition, crystalline-amorphous transitions and fracture phenomena related to the experimental mechanics of the nanomaterials are reviewed. Current limitations and future aspects using in situ high-resolution transmission electron microscopy of nanomaterials are also discussed. A new research field of in situ experimental mechanics at the atomic scale is thus expected. Keywords: atomic scale; dislocation; experimental mechanics; in situ; nanomaterial; twin INTRODUCTION Recent studies on nanostructured materials, including nanowires (NWs), 1,2 nanotubes (NTs), 1,3 nanocrystals (NC), 4 micro/nanopillars (NPs) 5-7 and nanocrystalline, 8,9 have revealed a variety of 'unusual deformation' phenomena compared with their bulk counterparts, such as high strength, nano-piezoelectric effects and unusual plastic deformation behaviors. Nanostructured materials can apparently sustain a larger dynamic range of elastic and plastic strains than conventional materials. The results from these studies indicate that the fundamental dislocation processes that initiate and sustain plastic flow and fracture in nanoscale materials are considerably different than in their conventional bulk counterparts. These 'unusual' phenomena not only allow these materials to possess excellent mechanical properties but also enable the tuning of their band structures and related novel electronic, magnetic, optical, photonic and catalytic properties. Revealing the atomic-scale deformation mechanisms of nanomaterials (NM) and controlling their elastic and plastic properties are useful for realizing the desired mechanical, physical and chemical properties through the application of stress or strain.Although extensive studies have been conducted to investigate the mechanical properties of NM, 10 the majority of the atomic

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Section: Direct Atomic Mechanisms Of the Size Effects On The Unusual mentioning

confidence: 99%

In situ experimental mechanics of nanomaterials at the atomic scale

2013

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“…on time-dependent deformation such as creep and fatigue [1]. It is known from literature that this behavior is affected by size-effects: the interaction between microstructural length scales and dimensional length scales [2,3]. Not much research has focused on characterizing size-effects in time-dependent material behavior, specifically for free-standing thin films [3].…”

Section: Discussionmentioning

confidence: 99%

Size-effects in time-dependent mechanics in metallic MEMS

Bergers

Delhey

Hoefnagels

et al. 2010

EPJ Web of Conferences

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SummaryReliability of microelectromechanical systems (MEMS) depends a.o. on time-dependent deformation such as creep and fatigue [1]. It is known from literature that this behavior is affected by size-effects: the interaction between microstructural length scales and dimensional length scales [2,3]. Not much research has focused on characterizing size-effects in time-dependent material behavior, specifically for free-standing thin films [3]. This study investigates size-effects caused by grain statistics in timedependent deformation in µm-sized free-standing aluminum cantilever beams.A numeric-experimental method is used to determine material parameters. The experiment entails applying a constant deflection to the micro-beams for a prolonged period. The deflection is achieved with 50 nm resolution via a micro-clamp. The beams are then released. Immediately the deformation evolution is recorded by acquiring surface height profiles with a confocal optical profiler. Image correlation of the full-field beam profiles is applied to correct for specimen drift and tilt. The experiment yields the tip deflection as function of time with ∼3 nm precision. In the numerical part, this data is combined with a finite element model based on a standard-solid material model. In this way material parameters describing time-dependent behavior are extracted. The time constant for the deflection evolution is determined within 20%, as verified by predicting a different experiment. Figure 1 shows the model and the numeric prediction of an experiment.To investigate the size-effects of grain statistics, orientation imaging microscopy (OIM) is employed directly on the free-standing cantilevers, see figure 2. This work correlates the obtained timedependent material parameters to the actual grain sizes, grain boundary length and texture orientation per specimen. Insights into the interplay between micro-mechanism and grain characteristic and the effect on the time-dependent material behavior are presented.

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“…This is most likely related to the difficulty to generate and move dislocations in these materials and ongoing research works are addressing this problem. The interested reader might find an introduction to this research field in [24][25][26][27][28].…”

Section: Microstructure and Propertiesmentioning

confidence: 99%