Abstract
Plastic deformation of small metallic single crystals has focused a lot of attention because of their enhanced or specific mechanical properties. Here, submicron beryllium wires, obtained from selective etching of an Al/Be eutectic alloy, were deformed in tension in situ using a transmission electron microscope. Our observations indicate that wires oriented parallel to their 〈c〉 axis and containing almost no dislocations present a fragile-like behavior associated to a high stress level. \(\left\{{10\bar 12} \right\}\) 〈1011〉 twins were also frequently observed near fractured wires, indicating that this deformation mode is important in small-scale Be. In a twinned area, a locally ductile behavior was observed due to the favorable orientation for prismatic slip. We also stress out the importance of a remaining outer layer, made of Al oxide, in the plastic deformation. On the basis of finite element modeling, we show that the deformation of the wire may involve dislocations moving along the wire axis, in or close to the Be/Al oxide interface, in agreement with in situ observations. Thus, even in naturally oxidized wires, the outer layer is supposed to play an important role in the deformation, not only in modifying a stress/strain field but also presumably in facilitating diffusional processes, such as dislocation climb or dislocation nucleation.
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O. Kraft, P.A. Gruber, R. Mönig, and D. Weygand: Plasticity in confined dimensions. Annu. Rev. Mater. Res. 40, 296 (2010).
J.R. Greer and J.T.M. De Hosson: Plasticity in small-sized metallic systems: Intrinsic versus extrinsic size effect. Prog. Mater. Sci. 56, 654 (2011).
H. Bei, S. Shim, G. Pharr, and E. George: Effects of pre-strain on the compressive stress–strain response of Mo-alloy single-crystal micropillars. Acta Mater. 56, 4762 (2008).
F. Mompiou, M. Legros, A. Sedlmayr, D. Gianola, D. Caillard, and O. Kraft: Source-based strengthening of sub-micrometer Al fibers. Acta Mater. 60, 977 (2012).
F. Mompiou and M. Legros: Plasticity mechanisms in sub-micron Al fiber investigated by in situ TEM. Adv. Eng. Mater. 14, 955 (2012).
D. Dunstan and A. Bushby: Grain size dependence of the strength of metals: The Hall–Petch effect does not scale as the inverse square root of grain size. Int. J. Plast. 53, 56 (2014).
P.S. Phani, K. Johanns, E. George, and G. Pharr: A simple stochastic model for yielding in specimens with limited number of dislocations. Acta Mater. 61, 2489 (2013).
J. Sharon, Y. Zhang, F. Mompiou, M. Legros, and K. Hemker: Discerning size effect strengthening in ultrafine-grained Mg thin films. Scr. Mater. 75, 10 (2014).
E. Lilleodden: Microcompression study of Mg (0001) single crystal. Scr. Mater. 62, 532 (2010).
C.M. Byer, B. Li, B. Cao, and K.T. Ramesh: Microcompression of single-crystal magnesium. Scr. Mater. 62, 536 (2010).
C.M. Byer and K. Ramesh: Effects of the initial dislocation density on size effects in single-crystal magnesium. Acta Mater. 61, 3808 (2013).
D.M. Norfleet: Sample size effects related to nickel, titanium and nickel-titanium at the micron size scale. Ph.D. thesis, Ohio State University, Columbus, Ohio, 2007.
Q. Yu, L. Qi, K. Chen, R.K. Mishra, J. Li, and A.M. Minor: The nanostructured origin of deformation twinning. Nano Lett. 12, 887 (2012).
J. Poirier, J. Antolin, and J. Dupouy: Investigations on some deformation modes of beryllium. Can. J. Phys. 45, 1221 (1967).
P. Regnier and J.M. Dupouy: Prismatic slip in beryllium and the relative ease of glide in HCP metals. Phys. Status Solidi 39, 79 (1970).
J. Beuers, S. Jonsson, and G. Petzow: Tem in situ deformation of beryllium single crystals—A new explanation for the anomalous temperature dependence of the critical resolved shear stress for prismatic slip. Acta Metall. 35, 2277 (1987).
A. Couret and D. Caillard: Prismatic slip in beryllium, i. the controlling mechanism at the peak temperature. Philos. Mag. A 59, 783 (1989).
F. Mompiou, M. Legros, C. Ensslen, and O. Kraft: In situ TEM study of twin boundary migration in sub-micron Be fibers. Acta Mater. 96, 57 (2015).
F. Mompiou and M. Legros: Quantitative grain growth and rotation probed by in situ TEM straining and orientation mapping in small grained Al thin films. Scr. Mater. 99, 5 (2015).
J.W. Cahn and J.E. Taylor: A unified approach to motion of grain boundaries, relative tangential translation along grain boundaries, and grain rotation. Acta Mater. 52, 4887 (2004).
A. Serra, D. Bacon, and R. Pond: Dislocations in interfaces in the h.c.p. metals—I. Defects formed by absorption of crystal dislocations. Acta Mater. 47, 1425 (1999).
M. Ignat, R. Bonnet, D. Caillard, and J. Martin: Creep of lamellar Al–CuAl2 composite. 1. Microstructural observations. Phys. Status Solidi A 49, 675 (1978).
J. Christian and S. Mahajan: Deformation twinning. Prog. Mater. Sci. 39, 1 (1995).
F. Mompiou and D. Caillard: Dislocation-climb plasticity: Modelling and comparison with the mechanical properties of icosahedral AlPdMn. Acta Mater. 56, 2262 (2008).
D.C. Van Aken and H.L. Fraser: The microstructures of rapidly solidified hyper-eutectic AlBe alloys. Acta Metall. 33, 963 (1985).
D.C. Van Aken: Crystallographic orientation relationships observed in rapidly solidified Al-Be alloys. In Dispersion Strengthened Aluminum Alloys, Y. Kim and W. Griffith, eds. (The Minerals, Metals & Materials Society, Pittsburgh, Pennsylvania, 1988).
K. Marukawa and Y. Matsubara: A new method of Burgers vector identification for grain boundary dislocations from electron microscopic images. Trans. Jpn. Inst. Met. 20, 560 (1979).
J.F. Smith and C.L. Arbogast: Elastic constants of single crystal beryllium. J. Appl. Phys. 31, 99 (1960).
K. Ng and A. Ngan: Effects of trapping dislocations within small crystals on their deformation behavior. Acta Mater. 57, 4902 (2009).
S-W. Lee, A.T. Jennings, and J.R. Greer: Emergence of enhanced strengths and Bauschinger effect in conformally passivated copper nanopillars as revealed by dislocation dynamics. Acta Mater. 61, 1872 (2013).
J.A. El-Awady, S.I. Rao, C. Woodward, D.M. Dimiduk, and M.D. Uchic: Trapping and escape of dislocations in micro-crystals with external and internal barriers. Int. J. Plast. 27, 372 (2011).
T. Balk, G. Dehm, and E. Artz: Parallel glide: Unexpected dislocation motion parallel to the substrate in ultrathin copper films. Acta Mater. 51, 4471 (2003).
L.Y. Chen, M. He, J. Shin, G. Richter, and D.S. Gianola: Measuring surface dislocation nucleation in defect-scarce nanostructures. Nat. Mater. 14, 707 (2015).
ACKNOWLEDGMENTS
The authors would like to thank L. Durand for her assistance in running FEM simulations and D. Lamirault for the sample preparation. This work has been supported by the French National Research Agency under the “Investissement d’Avenir” program reference No. ANR-10-EQPX-38-01.
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Mompiou, F., Legros, M. & Lartigue-Korinek, S. Deformation mechanisms in submicron Be wires. Journal of Materials Research 32, 4616–4625 (2017). https://doi.org/10.1557/jmr.2017.327
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DOI: https://doi.org/10.1557/jmr.2017.327