Size effects in strength and plasticity of single-crystalline titanium micropillars with prismatic slip orientation

Sun, Qiaoyan; Guo, Qiang; Yao, Xi; Lin, Xin; Greer, Julia R.; Sun, Jun

doi:10.1016/j.scriptamat.2011.05.033

Cited by 84 publications

(43 citation statements)

References 30 publications

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“…Fig. 8a shows the comparison of the maximum plastic strain and ultimate strength of AlN with other highstrength single crystals and amorphous alloys tested by micro-compression with pillar diameters ranging from $500 nm to 5 lm [22,25,[27][28][29][40][41][42][43][44]. The general trend from these data, regardless of deformation mechanisms, is that the higher strength of materials typically accompany with lower plasticity.…”

Section: Aln Micropillar Compression Along [1 0 1 0] Directionmentioning

confidence: 98%

“…Nevertheless, different from other ultra-high strength materials, the single-crystal AlN, especially (0 0 0 1) single crystals, shows an extraordinary combination of high strength and plasticity. Fig 8b summarizes the sample size effect on normalized strength of single crystals at a small length scale [22,25,[27][28][29][40][41][42], in which the shear strength (s) is normalized by the shear modulus (G) and fitted by a power law equation of sample diameters (d):…”

Section: Aln Micropillar Compression Along [1 0 1 0] Directionmentioning

confidence: 99%

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Sample size induced brittle-to-ductile transition of single-crystal aluminum nitride

et al. 2015

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Section: Aln Micropillar Compression Along [1 0 1 0] Directionmentioning

confidence: 98%

Section: Aln Micropillar Compression Along [1 0 1 0] Directionmentioning

confidence: 99%

Sample size induced brittle-to-ductile transition of single-crystal aluminum nitride

et al. 2015

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“…[13]. Data for hcp metals are more limited but Sun et al report (n % 0:5) for Ti in prism slip [14], while fitting to data in [15] yields n % 0:8 for basal slip in Mg compared to n % 0:4 from data in [16], again for basal slip, and n % 0:2 for pyramidal slip. Ignoring the data for Mg which shows considerable scatter it is interesting to note that in general n fcc > n hcp > n bcc whereas the bulk flow stress r bcc 0 > r hcp 0 > r fcc 0 .…”

Section: Introductionmentioning

confidence: 98%

A discrete dislocation plasticity study of the micro-cantilever size effect

et al. 2015

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Micro-cantilevers are increasingly used to extract elastic and plastic material properties through controlled bending using a nanoindenter. Focused Ion Beam milling can be used to produce small scale single crystal cantilevers with cross-sectional dimensions on the order of microns, and electron backscatter diffraction (EBSD) allows cantilevers to be milled from a grain with a desired crystal orientation. Micro-cantilever bending experiments suggest that sufficiently smaller cantilevers are stronger, which is generally believed to be related to the effect of the neutral axis on the evolution of the dislocation structure. A planar model of discrete dislocation plasticity was used to simulate end-loaded cantilevers to interpret the behaviour observed in experiments. The model allowed correlation of the initial dislocation source density and resulting slip band spacing to the experimental load displacement curve. There are similarities between the predictions of this model and those of earlier discrete dislocation plasticity models of pure bending. However, there are notable differences, including a strong source density dependence of the size effect that cannot be explained by geometrically necessary dislocation (GND) arguments, and the effect of the cantilever stress distribution on the locations of soft pile-ups. The planar model was used to identify zero resolved shear stress isolines, rather than the neutral axis, as controlling the soft pile-up location, and source spacing as limiting the slip band spacing in the observed size effect; strengthening was much greater in the source-limited regime. The effect of sample dimensions and dislocation source density were investigated and compared to small scale mechanical tests conducted on titanium and zirconium. The calculations predict a scaling exponent n % 1 for the dependence of stress on size if size is normalised by the average source spacing and a term representing the size-independent flow stress is included, whereas the simple power-law form ordinarily used to fit experimental data significantly underestimates n.

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“…Unlike bulk specimens, however, the multiplication of dislocations in micrometer-or submicrometer-sized pillars is difficult as dislocations travel a very short distance and ultimately escape from the free surfaces. Thus, micropillars or nanopillars tend to show strain softening or limited strain hardening [1,3,[30][31][32].…”

Section: Onset Of the Strain Bursts And Softening In Metals With Dimimentioning

confidence: 99%

Strategies to Approach Stabilized Plasticity in Metals with Diminutive Volume: A Brief Review

Mukherjee

Schoenung

et al. 2016

Crystals

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Abstract:Micrometer-or submicrometer-sized metallic pillars are widely studied by investigators worldwide, not only to provide insights into fundamental phenomena, but also to explore potential applications in microelectromechanical system (MEMS) devices. While these materials with a diminutive volume exhibit unprecedented properties, e.g., strength values that approach the theoretical strength, their plastic flow is frequently intermittent as manifested by strain bursts, which is mainly attributed to dislocation activity at such length scales. Specifically, the increased ratio of free surface to volume promotes collective dislocation release resulting in dislocation starvation at the submicrometer scale or the formation of single-arm dislocation sources (truncated dislocations) at the micrometer scale. This article reviews and critically assesses recent progress in tailoring the microstructure of pillars, both extrinsically and intrinsically, to suppress plastic instabilities in micrometer or submicrometer-sized metallic pillars using an approach that involves confining the dislocations inside the pillars. Moreover, we identify strategies that can be implemented to fabricate submicrometer-sized metallic pillars that simultaneously exhibit stabilized plasticity and ultrahigh strength.

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Size effects in strength and plasticity of single-crystalline titanium micropillars with prismatic slip orientation

Cited by 84 publications

References 30 publications

Sample size induced brittle-to-ductile transition of single-crystal aluminum nitride

Sample size induced brittle-to-ductile transition of single-crystal aluminum nitride

A discrete dislocation plasticity study of the micro-cantilever size effect

Strategies to Approach Stabilized Plasticity in Metals with Diminutive Volume: A Brief Review

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