A combined experimental and simulation study to examine lateral constraint effects on microcompression of single-slip oriented single crystals

Shade, Paul A.; Wheeler, Robert W.; Choi, Yoon Suk; Uchic, Michael D.; Dimiduk, Dennis M.; Fraser, Hamish L.

doi:10.1016/j.actamat.2009.06.029

Cited by 89 publications

(64 citation statements)

References 35 publications

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“…At the end of each strain burst, the pillar undergoes a short, nearly elastic loading until the stress is large enough to induce a new strain burst. This sporadic signature has been ubiquitously observed in the deformation of all nano and microscale pillars and is generally attributed to the highly stochastic nature of dislocation avalanches, and therefore, prevalent in sourcecontrolled plasticity [1][2][3][4][5][6][7][8][9][10][11]13,14,[16][17][18][19][36][37][38][39]. Importantly, these electroplated pillars share the same flow behavior as those produced by FIB, clearly demonstrating that the same deformation mechanisms likely govern flow behavior of nanoscale samples regardless of fabrication methods.…”

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confidence: 99%

Microstructure versus Size: Mechanical Properties of Electroplated Single Crystalline Cu Nanopillars

2010

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We report results of uniaxial compression experiments on single-crystalline Cu nanopillars with nonzero initial dislocation densities produced without focused ion beam (FIB). Remarkably, we find the same power-law size-driven strengthening as FIB-fabricated face-centered cubic micropillars. TEM analysis reveals that initial dislocation density in our FIB-less pillars and those produced by FIB are on the order of 10 14 m À2 suggesting that mechanical response of nanoscale crystals is a stronger function of initial microstructure than of size regardless of fabrication method.

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confidence: 99%

Microstructure versus Size: Mechanical Properties of Electroplated Single Crystalline Cu Nanopillars

2010

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“…Other experimental parameters can also have strong effects on the stress-strain curve, such as the lateral constrain imposed by the indenter. According to experimental evidence and crystal plasticity simulations in fee metals (Raabe et al, 2007;Shade et al, 2009), high lateral constrain results in lower yield stress and higher strain hardening because the large rotations in the constrained situation result in the activation of secondary slip systems. In addition, a breakdown of Schmid law in the case of sub-micron diameter pillars has been reported in crystals with a single family of slip systems due to the limited number of available dislocation sources when the diameter is reduced (Ng and Ngan, 2008a,b,c), which could result in stochastic activation of sources in nonpreferred slip systems.…”

Section: Effect Of Micropillar Size and Ion Irradiationmentioning

confidence: 99%

Micropillar compression of LiF [111] single crystals: Effect of size, ion irradiation and misorientation

Soler

Molina-Aldareguia

Segurado

et al. 2012

International Journal of Plasticity

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The mechanical response under compression of LiF single crystal micropillars oriented in the [111] direction was studied. Micropillars of different diameter (in the range 1-5 u.m) were obtained by etching the matrix in directionally-solidified NaCl-LiF and KCl-LiF eutectic compounds. Selected micropillars were exposed to high-energy Ga + ions to ascertain the effect of ion irradiation on the mechanical response. Ion irradiation led to an increase of approximately 30% in the yield strength and the maximum compressive strength but no effect of the micropillar diameter on flow stress was found in either the as-grown or the ion irradiated pillars. The dominant deformation micromechanisms were analyzed by means of crystal plasticity finite element simulations of the compression test, which explained the strong effect of micropillar misorientation on the mechanical response. Finally, the lack of size effect on the flow stress was discussed to the light of previous studies in LiF and other materials which show high lattice resistance to dislocation motion.

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“…Note that for single crystals the choice of boundary conditions is paramount, as the deformation response is far from axisymmetric. In a recent work Shade et al (2009) investigated the effects of boundary conditions on single crystal microcompression. Figure 9 gives the sample coordinate system and visualization for the grips.…”

Section: Boundary Conditionsmentioning

confidence: 99%

Dislocation subgrain structures and modeling the plastic hardening of metallic single crystals

Hansen

Bronkhorst

Ortiz

2010

Modelling Simul. Mater. Sci. Eng.

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A single crystal plasticity theory for insertion into finite element simulation is formulated using sequential laminates to model subgrain dislocation structures. It is known that local models do not adequately account for latent hardening, as latent hardening is not only a material property, but a nonlocal property (e.g. grain size and shape). The addition of the nonlocal energy from the formation of subgrain structure dislocation walls and the boundary layer misfits provide both latent and self-hardening of a crystal slip. Latent hardening occurs as the formation of new dislocation walls limits motion of new mobile dislocations, thus hardening future slip systems. Self-hardening is accomplished by an evolution of the subgrain structure length scale. The substructure length scale is computed by minimizing the nonlocal energy. The minimization of the nonlocal energy is a competition between the dislocation wall energy and the boundary layer energies. The nonlocal terms are also directly minimized within the subgrain model as they affect deformation response. The geometrical relationship between the dislocation walls and slip planes affecting the dislocation mean free path is taken into account, giving a firstorder approximation to shape effects. A coplanar slip model is developed due to requirements while modeling the subgrain structure. This subgrain structure plasticity model is noteworthy as all material parameters are experimentally determined rather than fit. The model also has an inherit path dependence due to the formation of the subgrain structures. Validation is accomplished by comparison with single crystal tension test results.

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A combined experimental and simulation study to examine lateral constraint effects on microcompression of single-slip oriented single crystals

Cited by 89 publications

References 35 publications

Microstructure versus Size: Mechanical Properties of Electroplated Single Crystalline Cu Nanopillars

Microstructure versus Size: Mechanical Properties of Electroplated Single Crystalline Cu Nanopillars

Micropillar compression of LiF [111] single crystals: Effect of size, ion irradiation and misorientation

Dislocation subgrain structures and modeling the plastic hardening of metallic single crystals

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