Compressive yield strengths of nanocrystalline Cu and Pd

Youngdahl, Carl J.; Sanders, Paul G.; Eastman, Jeffrey A.; Weertman, J.

doi:10.1016/s1359-6462(97)00157-7

Cited by 138 publications

(60 citation statements)

References 11 publications

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“…The dependences rðd À1=2 Þ taking into account respectively the only grain boundary diffusional creep (dashed curve) and both the grain boundary and triple junction Fig. 1) at small values of grain size d. Similar deviations are inherent to dependence observed experimentally [4][5][6]15,[36][37][38][39]) for mechanical characteristics (yield stress, microhardness) of real fine-grained copper materials (see Fig. 1).…”

Section: Resultssupporting

confidence: 67%

Triple junction diffusion and plastic flow in fine-grained materials

2002

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A theoretical model is suggested which describes the yield stress dependence on grain size in fine-grained materials, based upon competition between conventional dislocation slip, grain boundary diffusional creep (Coble creep) and triple junction diffusional creep. In the framework of the model, the contribution of diffusional creep mechanisms to plastic deformation increases with reduction of grain size, causing the abnormal Hall-Petch dependence in the range of small grains. A grain size distribution is incorporated into the consideration to account for a distribution of grain sizes occurring in real specimens. The results of the model are compared with experimental data from Cu and shown to be in good agreement. Ó

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Section: Resultssupporting

confidence: 67%

Triple junction diffusion and plastic flow in fine-grained materials

2002

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“…Hall-Petch relationships of nanocrystalline copper calculated by changing s ln v and the real data. [7][8][9][10][11][12] …”

Section: Discussionmentioning

confidence: 99%

“…This figure includes real data of nanocrystalline copper. [7][8][9][10][11][12] As understood from the figure, although the yield stress of real nanocrystalline copper is largely scattered, a lot of data are plotted in the region lying between the extremes of s ln v ¼ 1 and 2.5. This suggests that the wide scatter of data can be caused by the difference of s ln v .…”

Section: Effect Of Distribution Of Crystal Grains On Yield Stressmentioning

confidence: 99%

“…1,2) The appearance of bulk nanocrystalline materials in the 1980's 3) triggered a number of experimental studies of their mechanical behavior. [4][5][6][7][8][9][10][11][12][13][14] In the past decade, a variety of models have been proposed to rationalize the relationship between measurements of yield stress and mean grain size. [15][16][17][18][19][20] This study proposes a new micromechanics model to investigate the influence that dispersion in crystal grain sizes has upon the yield behavior of nanocrystalline materials.…”

Section: Introductionmentioning

confidence: 99%

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Micromechanics Model Concerning Yield Behavior of Nanocrystalline Materials

Morita

Mitra

Weertman³

2004

Mater. Trans.

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This analysis was conducted to investigate the influence that dispersion in crystal grain sizes has upon the yield behavior of nanocrystalline materials. In the model proposed for this purpose, the distribution of crystal grains was expressed in a log-normal manner. It was assumed that the yield stress of each crystal grain was determined by the relationship between the grain size and the stress required for the generation of dislocations from a grain boundary. Furthermore, using the micromechanics of inclusions, we carefully considered the internal stresses in the crystal grains yielded at a different remote applied stress and in the matrix which is still elastic. The result of the analysis showed that the increase of compliance with the yielding of crystal grains from large to small can cause the macroscopic yielding of nanocrystalline materials. It was also inferred that the distribution of crystal grains was one of the important factors which affect the shape of the stress-strain curve and the macroscopic yield stress.

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“…Since the stress state during a disk bend test is complex and involves both tensile and compressive stresses, it is possible that this may have an effect on the measured ductility of nanocrystalline materials. For example, significantly larger ductilities are seen for nanocrystalline Cu tested in compression [12] than in tension [8]. However, this cannot be the only reason for the measured enhanced ductility in case of n-NiAl, since coarse grained specimens did not show any evidence of ductility when also tested by BDBT under similar conditions.…”

Section: Resultsmentioning

confidence: 99%

Synthesis, Characterization and Mechanical Properties of Nanocrystalline NiAl

et al. 1996

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Nanocrystalline NiAl has been produced from pre-cast alloys using an electron beam inert gas condensation system. In-situ compaction was carried out at 100 to 300°C under vacuum conditions. Energy dispersive spectroscopy was used to determine chemical composition and homogeneity. Average grain sizes in the range of 4 to 10 nm were found from TEM dark field analyses. A compression-cage fixture was designed to perform disk bend tests. These tests revealed substantial room temperature ductility in nanocrystalline NiAl, while coarse grained NiAl showed no measurable room temperature ductility.

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Compressive yield strengths of nanocrystalline Cu and Pd

Cited by 138 publications

References 11 publications

Triple junction diffusion and plastic flow in fine-grained materials

Triple junction diffusion and plastic flow in fine-grained materials

Micromechanics Model Concerning Yield Behavior of Nanocrystalline Materials

Synthesis, Characterization and Mechanical Properties of Nanocrystalline NiAl

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