Inverse Hall–Petch behavior in diamantane stabilized bulk nanocrystalline aluminum

Maung, Khinlay; Earthman, James C.; Mohamed, Farghalli A.

doi:10.1016/j.actamat.2012.07.026

Cited by 54 publications

(12 citation statements)

References 47 publications

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“…Elemental Al is not widely used as a structural metal, with heavy alloying required to increase strength to an acceptable level even for use in aerospace applications, where limiting weight is the major priority. On the other hand, pure Al can be strengthened to levels comparable to steel alloys by grain refinement to the nanometer range [5]. Other advantages of nanostructuring include increased resistance to wear [6,7] and fatigue [8].…”

Section: Introductionmentioning

confidence: 99%

The role of complexions in metallic nano-grain stability and deformation

Rupert

2016

Current Opinion in Solid State and Materials Science

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Nanocrystalline metals have excellent strength due to the high density of grain boundaries inside. However, these same boundaries lead to limited thermal stability and a tendency to fail in a brittle manner, issues which limit the practical usage of these materials. Most strategies for stabilization of nano-grains against coarsening rely on the idea of using segregating dopants to lower excess boundary energy. The theory of interface complexions is a useful tool for describing the thermodynamics behind segregation as well as identifying distinct segregation patterns. Some of these same complexions can also dramatically alter mechanical behavior. Unlike past strategies, which always result in a trade-off between strength and ductility, the addition of complexions can potentially increase ductility while retaining or even increasing strength. In this paper, we discuss how complexions offer a unique opportunity to address these limitations simultaneously. In addition to reviewing the current-state-of-the-art, important areas where innovation is needed are also identified.

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Section: Introductionmentioning

confidence: 99%

The role of complexions in metallic nano-grain stability and deformation

Rupert

2016

Current Opinion in Solid State and Materials Science

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“…The result for the nano-grain size obtained in the present Al alloy is in agreement with the compiled data for cryomilling and the prediction of a dislocation model for minimum grain size obtainable via this severe deformation process [32]. Very recently, it was demonstrated that bulk nc-Al samples whose grain sizes are less than 100 nm can be produced by consolidating cryomilled Al powders containing diamantane [24], whose size is in the range of 2-5 nm, via hot isostatic pressing (HIP) followed by trap extrusion (high strain extrusion) at room temperature,; and that the average grain size for cryomilled bulk nc-Al containing diamantane was consistently about one half (69 nm) of that for the powders that do not contain diamantane at the same temperature (150 nm) [33].…”

Section: Resultsmentioning

confidence: 99%

Mechanical Characterization of Cryomilled Al Powder Consolidated by High-Frequency Induction Heat Sintering

El‐Danaf

Soliman

Almajid

et al. 2013

Advances in Materials Science and Engineering

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In the present investigation, an aluminum powder of 99.7% purity with particle size of ~45 µm was cryomilled for 7 hours. The produced powder as characterized by scanning, transmission electron microscopy, and X-ray diffraction gave a particle size of ~1 µm and grain (crystallite) size of23±6 nm. This powder, after degassing process, was consolidated using high-frequency induction heat sintering (HFIHS) at various temperatures for short periods of time of 1 to 3 minutes. The present sintering conditions resulted in solid compact with nanoscale grain size (<100 nm) and high compact density. The mechanical properties of a sample sintered at 773 K for 3 minutes gave a compressive yield and ultimate strength of 270 and 390 MPa, respectively. The thermal stability of grain size nanostructured compacts is in agreement with the kinetics models based on the thermodynamics effects.

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“…Experiments indicate a critical grain size dc at which the transition between the Hall-Petch effect and its reverse occurs (Chokshi et al 1989). This critical grain size is influenced by the temperature, for the aluminum alloy Al6061-T6 at room temperature this grain size is around 100 nm (Maung, Earthman and Mohamed 2012), and at that transition DM ceases. From the latter observation, and the dependence of GBS on d in eq.…”

Section: Grain Boundary Sliding Mechanismmentioning

confidence: 98%

“…(13) with the exception of d. Thus for d = d c , GBS = p and DM = 0. We now consider d = d 0 , where d 0 as above is the grain size prior to any refinement, in a situation where d c = 100 nm and d 0 = 75 µm as in the case of experimental data for Al6061-T6 (Shankar et al 2005, Maung et al 2012. In this situation, GBS ≈ 0, and DM ≈ p .…”

Section: Grain Boundary Sliding Mechanismmentioning

confidence: 99%

Latent heat saturation in microstructural evolution by severe plastic deformation

Bacca

McMeeking

2016

International Journal of Plasticity

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During plastic deformation, most of the dissipated work is released as heat, but a fraction of it, usually small, is stored in the microstructure, is called latent heat and is associated with the network of dislocations that develops. The rate of energy storage in the microstructure divided by the rate of plastic dissipation is defined as the latent heat capacity. Latent heat remains stored in the microstructure of cold worked specimens after quenching. This energy is associated with modified mechanical properties, e.g. hardness, and is released upon annealing. Saturation of this stored energy has been observed in experiments after a specific amount of plastic deformation is reached. A thermodynamically consistent model for continuous dynamic recrystallization is proposed in this paper with the aim of explaining the phenomenon of latent heat saturation and relating it to grain refinement. The proposed model has three essential features: (i) the latent heat increases in the specimen during plastic deformation as plastic work is continuously dissipated; (ii) the rate of latent heat storage per unit work, i.e. the latent heat capacity, is related to the internal architecture of the microstructure and decreases to zero as a consequence of microstructural evolution; (iii) the relationship between the latent heat and the microstructure is described through the use of two parameters: (a) the dislocation density and (b) the average grain diameter. A comparison of the proposed model with experiments is reported and a validation for the prediction of microstructural evolution, as well as the evolution of the latent heat and latent heat capacity, is provided.

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Inverse Hall–Petch behavior in diamantane stabilized bulk nanocrystalline aluminum

Cited by 54 publications

References 47 publications

The role of complexions in metallic nano-grain stability and deformation

The role of complexions in metallic nano-grain stability and deformation

Mechanical Characterization of Cryomilled Al Powder Consolidated by High-Frequency Induction Heat Sintering

Latent heat saturation in microstructural evolution by severe plastic deformation

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