Positive Deviation from a Hall-Petch Relation in Nanocrystalline Aluminum

Choi, Hyunjoo; Lee, S. W.; Park, J. S.

doi:10.2320/matertrans.mra2008343

Cited by 32 publications

(18 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As a consequence, a maximum threshold value of yield stress or hardness is generally reached at certain grain size level for a given nanocrystalline metal or alloy. Numerous reports show that the transition of positive to negative slope in the HP relationship is around 10-40 nm for varied nanocrystalline metals and alloys [6][7][8], such as Al [9][10][11], Fe [12], Cu [6,13,14], Cu-Ta [15], Ni [6], Ni-P [13], Zr [16], and Zn [17] among others.…”

Section: Introductionmentioning

confidence: 99%

Tensile nanomechanics and the Hall-Petch effect in nanocrystalline aluminium

Dávila

2018

Materials Science and Engineering: A

View full text Add to dashboard Cite

A B S T R A C TThis work carries out comprehensive classical molecular dynamics simulations of uniaxial tensile deformation for nanocrystalline Al samples with a broad range of different mean grain sizes. The largest nanocrystalline Al sample has a mean grain size of about 30 nm and contains over 100 millions atoms in the modeling system. The grain size dependence of yield stress and the atomic fraction of dislocations are quantified and the size dependence tensile nanomechanics are also revealed. Deformation twinning and grain boundary migration are observed as main mechanisms of tensile deformation in the nanocrystalline Al. In particular, the complete HallPetch relationship for the nanocrystalline Al bulk is determined for the first time in this study, from which three distinct regions are identified including the normal, inverse, and extended regions in the Hall-Petch relationship. We expect these findings will provide useful insights in the nanomechanics of nanocrystalline Al. The quantitation analyses on dislocations and mechanical properties may facilitate the design and development of high strength nanocrystalline Al and Al based alloys as well as future testing procedures for promising structural and transportation applications.

show abstract

Section: Introductionmentioning

confidence: 99%

Tensile nanomechanics and the Hall-Petch effect in nanocrystalline aluminium

Dávila

2018

Materials Science and Engineering: A

View full text Add to dashboard Cite

show abstract

“…As noted in Fig. 5, in this region, the yield stress of NC aluminum [22,24] does follow the dependence of d −1 rather than d −1/2 . As the grain size is further reduced to below 40nm, the calculated resolved shear stress for a partial dislocation becomes lower than that of a perfect dislocation, as shown in Fig.…”

Section: Resultsmentioning

confidence: 86%

“…In addition, it has also been experimentally observed that partial dislocations emitted from grain boundaries can travel the grain interior for thin films [9] and powders produced by cryogenic ball milling [13,21]. However, an experimental study using an extruded NC aluminum bulk has reported results that are completely opposite to a positive deviation from the Hall-Petch relation [22]. Recently, UFC aluminum fabricated by accumulative roll bonding has exhibited limited uniform elongation and unexpected yield-drop-like phenomenon [23], while it has not been observed in UFC aluminum having undergone powder metallurgy with similar grain sizes [24].…”

Section: Introductionmentioning

confidence: 67%

“…For aluminum with high SFE, perfect dislocations have been preliminarily observed in MD simulations rather than partial dislocations or intrinsic stacking fault only; a leading Shockley partial dislocation emitted from grain boundaries travels only to a splitting distance. Subsequently, a trailing partial dislocation emitted from grain boundaries reacts with a leading partial dislocation to be a perfect dislocation [21,22]. As noted in Fig.…”

Section: Resultsmentioning

confidence: 92%

“…In Fig. 5, yield stresses of aluminums, presented in this study and reported in other literatures [22,24,[27][28][29], are plotted as a function of grain size (d −1/2 ). Furthermore, calculated yield stresses based on the Hall-Petch equation [2], the deformation twin [13], the emission of partial and perfect dislocations [11], and grain boundary sliding [30] are also included.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

The Effect Of Grain Size On The Mechanical Properties Of Aluminum

Jeong¹,

Park²,

Nam³

et al. 2015

Archives of Metallurgy and Materials

View full text Add to dashboard Cite

Although many studies have focused on the unique plastic deformation behavior of nanocrystalline aluminum (e.g., the positive deviation from Hall-Petch relation, the unusual yield-drop phenomenon in tensile mode, etc.), the data reported by different research groups are inconsistent with each other, possibly because of different fabrication processes. In this study, aluminum samples with a wide grain-size spectrum -from a few micrometers down to 100 nanometers -are manufactured by powder metallurgy. The grain size was measured by X-ray diffraction analysis and transmission electron microscope observation. Furthermore, the tensile behavior, which varied according to a grain size, is discussed with a comparison of the theoretical models.

show abstract

The Hall–Petch and inverse Hall–Petch relations and the hardness of nanocrystalline metals

2019

View full text Add to dashboard Cite

We review some of the factors that influence the hardness of polycrystalline materials with grain sizes less than 1 lm. The fundamental physical mechanisms that govern the hardness of nanocrystalline materials are discussed. The recently proposed dislocation curvature model for grain size-dependent strengthening and the 60-year-old Hall-Petch relationship are compared. For grains less than 30 nm in size, there is evidence for a transition from dislocationbased plasticity to grain boundary sliding, rotation, or diffusion as the main mechanism responsible for hardness. The evidence surrounding the inverse Hall-Petch phenomenon is found to be inconclusive due to processing artefacts, grain growth effects, and errors associated with the conversion of hardness to yield strength in nanocrystalline materials.

show abstract

Positive Deviation from a Hall-Petch Relation in Nanocrystalline Aluminum

Cited by 32 publications

References 28 publications

Tensile nanomechanics and the Hall-Petch effect in nanocrystalline aluminium

Tensile nanomechanics and the Hall-Petch effect in nanocrystalline aluminium

The Effect Of Grain Size On The Mechanical Properties Of Aluminum

The Hall–Petch and inverse Hall–Petch relations and the hardness of nanocrystalline metals

Contact Info

Product

Resources

About