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iDEA: Drexel E-repository and Archives > Drexel Academic Community > College of Engineering > Department of Materials Science and Engineering > Faculty Research and Publications (MSE) > Deformation micromechanisms of ZnO single crystals as determined from spherical nanoindentation stress-strain curves

Please use this identifier to cite or link to this item: http://hdl.handle.net/1860/1895

Title: Deformation micromechanisms of ZnO single crystals as determined from spherical nanoindentation stress-strain curves
Authors: Barsoum, Michel W.
Sandip, Basu
Keywords: Kink bands;Mechanical-properties;Ti3SiC2;Indentations;Films
Issue Date: 2007
Publisher: Materials Research Society
Citation: Journal of Materials Research, 22(9): pp. 2470-2477.
Abstract: In this work, instrumented nanoindentation experiments with two spherical tips with radii of 13.5 and 1 mu m were used to explore the deformation behavior of ZnO single crystals with two orientations, C (basal) and A (prism). By converting the nanoindentation load-displacement data to stress-strain curves, we show that the main reason the hardening rates are higher for the C plane than they are for the A plane is the activation of dislocations-with widely different flow stresses-on different sets of slip planes. For the former, glide occurs on basal planes as well as pyramidal planes; for the latter, glide occurs predominantly on basal planes. The C plane is roughly twice as hard as the A plane, probably due to the orientation of basal planes with respect to the indentation axis. A Weibull statistical analysis of the pop-in stresses indicates that the inherent defect concentration at or near the surface is the main factor for the initiation of plastic deformation. The strain energy released when the pop-ins occur determines their extent. The elastic moduli values, determined by Berkovich nanoindentation, are 135 +/- 3 GPa and 144 +/- 4 GPa for the C and A planes, respectively. In the C orientation repeated indentations to the same stress result in fully reversible hysteretic loops that are attributed to the formation of incipient kink bands.
URI: http://dx.doi.org/10.1557/JMR.2007.0305
http://hdl.handle.net/1860/1895
Appears in Collections:Faculty Research and Publications (MSE)

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