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 language | English (US) |
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Pages (from-to) | 178-191 |
Number of pages | 14 |
Journal | Acta Materialia |
Volume | 72 |
DOIs | |
State | Published - 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