Microstructural evolutions and stability of gradient nano-grained copper under tensile tests and subsequent storage

Chen, W; You, Zhifeng; Tao, Nengguo; Lü, Lei

doi:10.1088/1757-899x/89/1/012001

Cited by 8 publications

(5 citation statements)

References 27 publications

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“…The rate-controlled mechanism seems not only useful to address the grain coarsening normally observed in a variety of NG samples under mechanical deformation [12,13], but also provide further clues to understand the abnormal grain coarsening at low temperatures without mechanical loading [5,6].To optimize the mechanical performance of NG materials, e.g. in terms of the trade-off between strength and ductility, it is essential to stabilize the NG structure at elevated temperatures.…”

Section: Mechanically-induced Grain Coarsening Kinetics-further Issuesmentioning

confidence: 99%

“…Softening due to grain coarsening or grain growth seems spontaneous and inevitable in many NG metals when the specimen is held at or even below the room temperature (RT) [5,6]. In particular, such "unusual" grain coarsening may occur more readily under mechanical deformation (termed as mechanically-induced grain coarsening), as observed in the indentation [7][8][9], rolling [10], compression [11] and tensile loading [12,13] tests.…”

Section: Introductionmentioning

confidence: 99%

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Mechanically-induced grain coarsening in gradient nano-grained copper

et al. 2017

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Gradient nano-grained Cu subjected to tensile tests yields at a stress almost twice of that of the conventional coarse-grained Cu at or below the room temperature. Beyond the yield stress, a uniform plastic strain of larger than 30% can be achieved, accompanied by homogeneous grain coarsening in nano-grained surface layer.The observed grain coarsening may induce certaindegree of "strain softening". The measured grain coarsening rates strongly depend on temperature, stress and strain rate, suggesting that the grain coarsening is presumably limited by thermally activated dislocation activities at defective grain boundaries, rather than via diffusional process on atom-by-atom basis. A non-diffusional (source-limited) Mott-Turnbull rate equation has been proposed to interpret the observed grain coarsening phenomenon.

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Section: Mechanically-induced Grain Coarsening Kinetics-further Issuesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mechanically-induced grain coarsening in gradient nano-grained copper

et al. 2017

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“…[50] GB relaxation was induced in single-phased multicomponent Ni-Co-Cr alloys as grains are refined below 30 nm through plastic deformation. [52] The stabilized GB-networks that are interlocked with abundant twin boundaries inhibit significantly diffusional creep [25,[47][48][49] are included for comparison. (Reprinted with permission from Ref.…”

Section: Gb Relaxation In Nanograined Alloysmentioning

confidence: 99%

“…3-Relative grain size change (D D/D 0 ) with respect to initial average grain size (D 0 ) in the gradient nanograined Cu samples after tension. Data from the literatures[25,[47][48][49] are included for comparison. (Reprinted with permission from Ref [46]…”

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confidence: 99%

A Novel Metastable Structure in Polycrystalline Metals With Extremely Fine Grains: Schwarz Crystal

2023

Metall Mater Trans A

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Most metals exist in form of polycrystalline states consisting of crystalline grains and grain boundaries. These structurally defective boundaries make the materials thermodynamically unstable. Upon heating or straining, polycrystalline metals tend to be stabilized by eliminating grain boundaries through grain coarsening or transforming into metastable glassy phases when the grains are very small. Recently, we found a different metastable structure in polycrystalline face-centered-cubic pure metals and alloys as their grains are refined to a few nanometers with cryogenic high-pressure torsion. In this structure, named as ''Schwarz crystal'', the grain boundary networks evolved into the 3D periodical minimal surface structures constrained with high density twin-boundaries. It is thermally so stable that grain coarsening is inhibited at temperatures around the melting point, and exhibits a strength close to the theoretical value. Diffusional processes in alloys like precipitation of intermetallic phase, spinodal decomposition, as well as melting are inhibited with the Schwarz crystal structure. This paper briefly reviews the discovery of this novel metastable structure. The precursory process (grain boundary relaxation) in nanograined metals, formation and structure characteristics of the Schwarz crystals, as well as their thermal stability and strength in different metals and alloys will be introduced with experimental and molecular dynamic simulations. Perspectives and future studies on the structure will be discussed.

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“…Data from T-GBR samples after tension with a strain of 0.3 are presented as stars. Data from the literature [151][152][153] are included for comparison. 144…”

Section: Conclusion and Future Outlookmentioning

confidence: 99%

Stability of nanocrystalline metals: The role of grain-boundary chemistry and structure

Schuh

2021

MRS Bulletin

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Nanocrystalline metals are transitioning from laboratory curiosities to engineering materials, in large part due to advances in improving their stability, making their exceptional properties more predictable and accessible. Nanoscale grains typically have a very strong innate tendency to coarsen, but the grain-boundary structure can be designed and tuned to lower its excess energy, reducing both the driving force for coarsening and the grain-boundary mobility. This article reviews two major strategies for achieving low-energy grain boundaries in nanocrystalline structures. First, grain-boundary alloying is discussed, including grainboundary segregation and its energetic competition with the formation of second phases; with sufficient grain-boundary segregation tendency it is possible to stabilize nanostructures to high temperatures. Second, methods of achieving low-energy crystallographic grainboundary structures are discussed, including the formation of nanotwinned structures and relaxing grain boundaries into low-energy structures through their interactions with partial dislocations. Both of these strategies have led to effective and implementable stable nanocrystalline materials, and point to many directions for future advancements.

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Microstructural evolutions and stability of gradient nano-grained copper under tensile tests and subsequent storage

Cited by 8 publications

References 27 publications

Mechanically-induced grain coarsening in gradient nano-grained copper

Mechanically-induced grain coarsening in gradient nano-grained copper

A Novel Metastable Structure in Polycrystalline Metals With Extremely Fine Grains: Schwarz Crystal

Stability of nanocrystalline metals: The role of grain-boundary chemistry and structure

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