Nanotwinned fcc metals: Strengthening versus softening mechanisms

Stukowski, Alexander; Albe, Karsten; Farkas, Diana

doi:10.1103/physrevb.82.224103

Cited by 126 publications

(66 citation statements)

References 35 publications

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“…Both experimental and theoretical efforts have been made in investigating the deformation behavior of nt Cu subjected to different loading modes, including tension, rolling, and nanoindentation. [3][4][5][6][7][8][9][10][11][12] It is found that the high strength of nt Cu is a result of TBs acting as effective obstacles to dislocation motion, while the eminent ductility is owing to the enhanced dislocation nucleation sites provided by TBs. To date, limited information is known about the deformation mechanism of nt Cu during wear process.…”

Section: Introductionmentioning

confidence: 99%

Twin boundary spacing-dependent friction in nanotwinned copper

et al. 2012

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The deformation mechanisms of nanotwinned Cu subjected to nanoscratching are investigated by means of molecular dynamics simulations. Scratching simulations on nanotwinned single-crystalline Cu with the twin planes parallel and perpendicular to the scratching direction are performed. Since the detwinning mechanism is completely suppressed in the former case, no apparent correlation between frictional coefficient and the twin spacing is observed. In samples where the twin planes are perpendicular to the scratching direction, the friction increases as the twin spacing decreases, and then decreases as the twin spacings become even smaller. It results from the competitive plastic deformation between the inclined dislocations and the detwinning mechanism. Subsequent simulations for nanotwinned polycrystalline Cu unveil that in addition to the grainboundary-associated deformation mechanism, dislocation-mediated detwinning plays a significant role in the plastic deformation of nanotwinned Cu. The twin boundary spacing in turn affects nanotwinned materials to resist scratching via plastic deformation. We demonstrate via the nanoscratching tests that there exists a critical twin boundary spacing for which the friction coefficient is maximized and that this transition results from the competing deformation mechanisms in those nanotwinned materials.

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Section: Introductionmentioning

confidence: 99%

Twin boundary spacing-dependent friction in nanotwinned copper

et al. 2012

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“…182,183 Dislocation pileups at the GB in nc Cu are predicted to form in grain sizes above 50 nm. 184 As a complement to highly twinned electrodeposited structures, more recent studies have focused on the mechanical behavior and stability of nanocrystalline structures with a high density of twins, [185][186][187][188][189] whereby the twins provide obstacles to dislocation motion as well as dislocation nucleation sites within ''Bulk'' Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys the nanocrystalline grain structure. The deformation mechanisms observed in these MD simulations qualitatively agree with limited experimental results.…”

Section: Nanocrystalline MD Simulationsmentioning

confidence: 99%

“Bulk” Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

Tschopp

Murdoch

Kecskes

et al. 2014

JOM

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It is a new beginning for innovative fundamental and applied science in nanocrystalline materials. Many of the processing and consolidation challenges that have haunted nanocrystalline materials are now more fully understood, opening the doors for bulk nanocrystalline materials and parts to be produced. While challenges remain, recent advances in experimental, computational, and theoretical capability have allowed for bulk specimens that have heretofore been pursued only on a limited basis. This article discusses the methodology for synthesis and consolidation of bulk nanocrystalline materials using mechanical alloying, the alloy development and synthesis process for stabilizing these materials at elevated temperatures, and the physical and mechanical properties of nanocrystalline materials with a focus throughout on nanocrystalline copper and a nanocrystalline Cu-Ta system, consolidated via equal channel angular extrusion, with properties rivaling that of nanocrystalline pure Ta. Moreover, modeling and simulation approaches as well as experimental results for grain growth, grain boundary processes, and deformation mechanisms in nanocrystalline copper are briefly reviewed and discussed. Integrating experiments and computational materials science for synthesizing bulk nanocrystalline materials can bring about the next generation of ultrahigh strength materials for defense and energy applications.

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“…28,29 Uniform uniaxial deformation of NT Cu has been investigated previously using both experiments and MD simulations. [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] Interestingly, the strength of such NT Cu was found to first increase with decreasing twin-boundary spacing (TBS), reaching a maximal strength at a critical twin thickness, then decrease with further reduced twin thickness due to a transition of deformation mechanisms from the classical Hall-Petch type strengthening to a dislocation-nucleationcontrolled softening with twin-boundary migration. 29,41 Harder and tougher materials under shock loading could offer novel applications, such as improved armor materials.…”

Section: Introductionmentioning

confidence: 99%

Shock response of nanotwinned copper from large-scale molecular dynamics simulations

Yuan

2012

Phys. Rev. B

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A series of large-scale molecular dynamics simulations have been performed to investigate the shock response of nanotwinned (NT) Cu, including shock-induced plasticity, strength behind the shock front, and spall behaviors. In this study, two configurations were investigated at an impact velocity of 600 m/s, i.e., the practical NT polycrystalline Cu with an average grain size of 10 nm and the simple NT single-crystalline Cu with an impact direction of [112]. In the NT polycrystalline Cu, the average flow stress behind the shock front first increases with decreasing twin-boundary spacing (TBS), reaching a maximum at a critical TBS, and then decreases as the TBS become even smaller. This trend of the average flow stress with decreasing TBS is due to two competitive dislocation activities under shock loading, with one being inclined to the twin boundaries (the dislocation-twin boundary intersecting) and the other parallel to the twin boundaries (detwinning with twin-boundary migration). Since voids always nucleate near the grain boundary (GB) junctions and then grow along the GBs to create spallation, no apparent correlation between the spall strength and TBS is observed in the NT polycrystalline Cu. However, the spall strengths of the NT single-crystalline Cu are found to increase with decreasing TBS. Two partial dislocation slips initiated from each twin boundary create voids at the intersections between the partial dislocation slips and twin boundaries. The smaller TBSs result in a larger number of twin boundaries and provide more nucleation sites for voids, requiring a higher tensile stress to create spallation in the NT single-crystalline Cu. These findings should provide insights for understanding the deformation physics of the NT metals subjected to shock loading.

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Nanotwinned fcc metals: Strengthening versus softening mechanisms

Cited by 126 publications

References 35 publications

Twin boundary spacing-dependent friction in nanotwinned copper

Twin boundary spacing-dependent friction in nanotwinned copper

“Bulk” Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

Shock response of nanotwinned copper from large-scale molecular dynamics simulations

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