Plasticity in the nanoscale Cu/Nb single-crystal multilayers as revealed by synchrotron Laue x-ray microdiffraction
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Seung-Min Hanb) Department of Materials Science & Engineering, Stanford University, Stanford, California 94305; and Graduate School of Energy, Environment and Water Sustainability, Korea Advanced Institute of Science & Technology, Daejeon 305-701, Republic of Korea
Nan Li, Qiang-Min Wei, and Patricia Dickerson Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545
Nobumichi Tamura and Martin Kunz Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720
Amit Misra Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (Received 30 June 2011; accepted 11 October 2011)
There is much interest in the recent years in the nanoscale metallic multilayered composite materials due to their unusual mechanical properties, such as very high flow strength and stable plastic flow to large strains. These unique mechanical properties have been proposed to result from the interface-dominated plasticity mechanisms in nanoscale composite materials. Studying how the dislocation configurations and densities evolve during deformation will be crucial in understanding the yield, work hardening, and recovery mechanisms in the nanolayered materials. In an effort to shed light on these topics, uniaxial compression experiments on nanoscale Cu/Nb single-crystal multilayer pillars using ex situ synchrotron-based Laue x-ray microdiffraction technique were conducted. Using this approach, we studied the nanoscale Cu/Nb multilayer pillars before and after uniaxial compression to about 14% of plastic strain and found significant Laue peak broadening in the Cu phase, which indicates storage of statistically stored dislocations, while no significant Laue peak broadening was observed in the Nb phase in the nanoscale multilayers. These observations suggest that at 14% plastic strain of the nanolayered pillars, the deformation was dominated by plasticity in the Cu nanolayers and elasticity or possibly a zero net plasticity (due to the possibility of annihilation of interface dislocations) in the Nb nanolayers.
I. INTRODUCTION
Studying the deformation mechanisms in the nanoscale metallic multilayered composite materials has increasingly become both an interesting topic scientifically and an important subject technologically during these recent years, especially with the oncoming development of the new generations of nuclear energy systems. Nanoscale metallic multilayered composite materials are interesting due to their unusual mechanical properties such as very high flow strength and stable plastic flow to large strains.1–3 The interface-dominated plasticity mechanisms a)
Address all correspondence to this author. e-mail: [email protected] b) This author was an editor of this focus issue during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs. org/jmr-editor-manuscripts/ DOI: 10.1557/jmr.2011.421 J. Mater. Res., Vol. 27, No. 3, Feb 14
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