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Size effects in LiF micron-scale single crystals of low dislocation density

Published online by Cambridge University Press:  31 January 2011

Edward M. Nadgorny ,
Dennis M. Dimiduk  and
Michael D. Uchic
Edward M. Nadgorny*
Affiliation:
General Dynamics Information Technology, Dayton, Ohio 45431-1231
Dennis M. Dimiduk
Affiliation:
Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433-7817
Michael D. Uchic
Affiliation:
Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433-7817
*
a)Address all correspondence to this author. e-mail: [email protected] On sabbatical leave from Physics Department, Michigan Technological University, Houghton, MI 49931.
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Abstract

This study examines the size-dependent deformation response of pure LiF single crystals using microcompression testing. Microcrystals with an 〈001〉 orientation and sample diameter D ranging from 1 to 20 μm were fabricated by focused ion beam (FIB)-milling from bulk crystals having a low initial dislocation density. Both as-grown and γ-irradiated crystals were examined to characterize the effect of an increased point defect density on the size-affected plastic flow response. Similar to previously studied face-centered cubic (FCC)-derivative metals, both types of LiF microcrystals exhibit typical size-dependent plastic flow behavior: a dramatic size-dependent and statistically varying flow stress, atypically high strain hardening rates at small plastic strains, and fast intermittent strain bursts. The size-dependent strengthening obeys a power law, σ ∼ D−m, where m ≈ 0.8, and this rapid hardening results in engineering flow stresses of 650 MPa in 1-μm samples. The findings are evaluated against possible dislocation mechanisms that could be responsible for the observed size effects.

Keywords

DislocationsNanoscaleStress/strain relationship
Type
Outstanding Symposium Papers
Information
Journal of Materials Research , Volume 23 , Issue 11 , November 2008 , pp. 2829 - 2835
Copyright
Copyright © Materials Research Society 2008

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References

REFERENCES

1Uchic, M.D., Dimiduk, D.M., Florando, J., Nix, W.D.: Sample dimensions influence strength and crystal plasticity. Science 305, 986 2004Google Scholar
2Uchic, M.D., Dimiduk, D.M.: A methodology to investigate size scale effects in crystalline plasticity using uniaxial compression testing. Mater. Sci. Eng., A 400–401, 268 2005Google Scholar
3Dimiduk, D.M., Uchic, M.D., Parthasarathy, T.A.: Size-affected single-slip behavior of pure nickel microcrystals. Acta Mater. 53, 4065 2005Google Scholar
4Norfleet, D.M., Dimiduk, D.M., Polasik, S.J., Uchic, M.D., Mills, M.J.: Dislocation structures and their relationship to strength in deformed nickel microcrystals. Acta Mater. 56, 2988 2008Google Scholar
5Johnston, W.G., Gilman, J.J.: Dislocation velocities, dislocation densities, and plastic flow in lithium fluoride crystals. J. Appl. Phys. 30, 129 1959Google Scholar
6Dimiduk, D.M., Woodward, C., LeSar, R., Uchic, M.D.: Direct measurement of scale-free intermittent flow in crystal plasticity. Science 312, 1188 2006CrossRefGoogle Scholar
7Miguel, M.-Carmen, Vespignani, A., Zapperi, S., Weiss, J., Grasso, J-R.: Intermittent dislocation flow in viscoplastic deformation. Nature 410, 667 2001CrossRefGoogle ScholarPubMed
8Richeton, T., Dobron, P., Chmelik, F., Weiss, J., Louchet, F.: On the critical character of plasticity in metallic single crystals. Mater. Sci. Eng., A 424, 190 2006Google Scholar
9Zaiser, M., Madani-Grasset, F., Koutsos, V., Aifantis, E.C.: Self-affine surface morphology of plasticity deformed metals. Phys. Rev. Lett. 93, 195507 2004Google Scholar
10Nadgorny, E.M., Schwerdtfeger, J., Madani-Grasset, F., Koutsos, V., Aifantis, E.C., Zaiser, M.: Evolution of self-affine surface roughness in plastically deforming KCl single crystals in Statistical Mechanics of Plasticity and Related Instabilities, edited by M. Zaiser, A. El-Azab, S. Dattagupta, S.B. Krupanidhi, S. Noronha, and S.S. Shivashankar PoS Proc. of Intl. Conference SMPRI2005 012, 1 2005Google Scholar
11Schwerdtfeger, J., Nadgorny, E., Koutsos, V., Blackford, J., Zaiser, M.: Scale-free statistics of plasticity-induced surface steps on KCl single crystals. J. Stat. Mech.: Theory Exp. L04001 2007Google Scholar
12Zaiser, M.: Scale invariance in plastic flow of crystalline solids. Adv. Phys. 55, 185 2006Google Scholar
13Zaitsev, S.I., Nadgorny, E.M.: Kinetics of motion of slip bands in NaCl crystals. Sov. Phys. Solid State 14, 2787 1973Google Scholar
14Zaitsev, S.I., Nadgorny, E.M.: Computer simulation of thermally activated dislocation motion through a random array of point obstacles. Nucl. Metal 20, 707 1976Google Scholar
15Nadgorny, E.M.: Dislocation Dynamics and Mechanical Properties of Crystals Vol. 31 edited by J.W. Christian, P. Haasen, and T.B. Massalski Pergamon Press Oxford 1988Google Scholar
16Paczuski, M., Maslov, S., Bak, P.: Avalanche dynamics in evolution, growth, and depinning models. Phys. Rev. E 53, 414 1996Google Scholar
17Newman, M.E.J.: Power laws, Pareto distributions and Zipf’s law. Contemp. Phys. 46, 323 2005CrossRefGoogle Scholar
18Sevillano, J. Gil, Ocana, A.I., Kubin, L.P.: Intrinsic size effects in plasticity by dislocation glide. Mater. Sci. Eng., A 309–310, 393 2001Google Scholar
19Parthasarathy, T.A., Rao, S.I., Dimiduk, D.M., Uchic, M.D., Trinkle, D.R.: Contribution to size effect of yield strength from the stochastics of dislocation source lengths in finite samples. Scr. Mater. 56, 313 2007Google Scholar
20Rao, S.I., Parthasarathy, T.A., Tang, M., Dimiduk, D.M., Uchic, M.D., Woodward, C.: Athermal mechanisms of size-dependent crystal flow gleaned from three-dimensional discrete dislocation simulations. Acta Mater. 56, 3245 2008Google Scholar
21Nadgorny, E.M., Dimiduk, D.M., Uchic, M.D., Rao, S.I., Parthasarathy, T.A., Woodward, C.: 2008, in preparationGoogle Scholar
22Segall, D.E., Li, C., Xu, G.: Corroboration of a multiscale approach with all atom calculations in analysis of dislocation nucleation from surface steps. Philos. Mag. 86, 5063 2006Google Scholar
23Jackson, D.P.: Surface relaxation in cubic metals. Can. J. Phys. 49, 2093 1973Google Scholar
24Smirnov, B.I.: Average dislocation nucleation distance during the formation of slip lines in LiF crystals. Sov. Phys. Solid State 9, 319 1967Google Scholar
25Smirnov, B.I.: Dislocation Structure and Crystal Hardening Nauka Moscow 1981Google Scholar