Microstructural evolution of nanolayered Cu-Nb composites subjected to high-pressure torsion

E. H. Ekiz, T. G. Lach, R. S. Averback, N. A. Mara, I. J. Beyerlein, M. Pouryazdan, H. Hahn, P. Bellon

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Abstract

Bulk nanolayered Cu/Nb composites fabricated by accumulative roll bonding (ARB), leading to a nominal layer thickness of 18 nm, were subjected to large shear deformation by high-pressure torsion at room temperature. The evolution of the microstructure was characterized using X-ray diffraction, transmission electron microscopy and atom probe tomography. At shear strains of ∼4, the crystallographic texture started to change from the one stabilized by ARB, with a Kurdjumov-Sachs orientation relationship and a dominant {1 1 2} Cu||{1 1 2}Nb interface plane, toward textures unlike the shear texture of monolithic Cu and Nb. At larger strains, exceeding 10, the initial layered structure was progressively replaced by a three-dimensional Cu-Nb nanocomposite. This structure remained stable with respect to grain size, morphology and global texture from strains of ∼290 to the largest ones used in this study, 5900. The three-dimensional self-organized nanocomposites comprised biconnected Cu-rich and Nb-rich regions, with a remarkably small coexistence length scale, ∼10 nm. The results are discussed in the context of the effect of severe plastic deformation and strain path on microstructure and texture stability in highly immiscible alloy systems.

Original languageEnglish (US)
Pages (from-to)178-191
Number of pages14
JournalActa Materialia
Volume72
DOIs
StatePublished - Jun 15 2014

Bibliographical note

Funding Information:
This work was supported as part of the Center for Materials at Irradiation and Mechanical Extremes, an Energy Frontier Research Center funded by the U.S. Department of Energy , Office of Science , Office of Basic Energy Sciences under Award Number 2008LANL1026. APT was performed at the Northwestern University Center for Atom-Probe Tomography (NUCAPT) whose local-electrode atom-probe (LEAP) tomograph was purchased and upgraded with funding from NSF-MRI ( DMR-0420532 ) and ONR-DURIP ( N00014-0400798 , N00014-0610539 , N00014-0910781 ) Grants. Instrumentation at NUCAPT was supported by the Initiative for Sustainability and Energy at Northwestern (ISEN). NUCAPT is a Shared Facility at the Materials Research Center of Northwestern University, supported by the National Science Foundation’s MRSEC program (DMR-1121262. Stimulating discussions with Drs. A. Misra and J. Carpenter (LANL), and Prof. A. Rollett (CMU), are gratefully acknowledged.

Keywords

  • Copper alloys
  • High-pressure torsion
  • Nanocomposite
  • Niobium alloys
  • Severe plastic deformation

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