Thermal Stability of the High Strength High Conductivity Cu–Nb, Cu–V, and Cu–Fe Nanostructured Microcomposite Wires (original) (raw)
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IEEE Transactions on Applied Superconductivity, 2010
The nanostructured microcomposites with FCC (Face Centered Cubic lattice) copper metal matrix and BCC (Body Centered Cubic lattice) metal strengthening filaments uniformly distributed in copper matrix are characterized by specific unique combination of physical and mechanical properties that distinctly differs from the properties of coarse grained macrocomposite materials. The experimental investigation on the influence of the nature of BCC strengthening elements is presented. Cu-Nb, Cu-V and Cu-Fe microcomposite wires have been designed and produced with the use of the same fabrication approach. The main mechanisms of microstructure transformation for all three composite materials have been analyzed. The possibility to attain the optimum microstructure with extremely high volume fraction of internal phase boundaries for each of the investigated microcomposites has been estimated. The data on the mechanical strength and electrical conductivity of Cu-Nb, Cu-V and Cu-Fe microcomposites are presented. The correlations the attained mechanical strength and conductivity with microstructure parameters are analyzed.
Microstructural characterization of high strength high conductivity Cu-Nb microcomposite wires
Purpose: The properties and the microstructure of cold drown Cu-Nb composites have been investigated for their potential use as conductors in high field magnets. Nowadays, there is much activity in the development of such conductors all over the world. Design/methodology/approach: This study was aimed to investigate microstructure, mechanical and electrical properties of Cu-Nb15 wires. The investigated materials have been processed by vacuum furnace melting and casting, further hot forging and cold drawing. Alternatively material has been processed by one of the SPD (severe plastic deformation) method using oscillatory turning die pressing. Microstructure has been observed by optical and electron microscopy technics. Findings: The ultimate tensile strength versus cold deformation degree have been presented. These changes have been discussed in relation to the microstructure evolution. Practical implications: The obtained mechanical and electrical properties (UTS over 900 MPa and ele...
Plasticity Mechanisms in Multi-Scale Copper-Based Nanocomposite Wires
Materials Science Forum, 2007
Copper-based high strength nanofilamentary wires reinforced by Nb nanofilaments are prepared by severe plastic deformation (repeated hot extrusion, cold drawing and bundling steps) for the winding of high pulsed magnets. The effects of microstructure refinement on the plasticity mechanisms were studied via nanoindentation, in-situ deformation in TEM and under neutron beam: all results evidence size effects in each nanostructured phase of the nanocomposite wires, i.e. single dislocation regime in the finest regions of the Cu matrix and whisker-like behaviour in the Nb nanofilaments. The macroscopic high yield stress is thus the results of the combination of the different elastic-plastic regimes of each phase that include size effects.
Russian Metallurgy (Metally), 2010
The influence of cold rolling and subsequent annealing at different temperatures on the micro structure, strength properties, and electrical conductivity of a microcomposite Cu-18% Nb alloy fabricated by bundling and deformation is studied. A composite billet is rolled up to a total true strain of 3.5 and 5.1. After rolling, a nanocrystalline structure is obtained with an average filament width of 70-100 nm depending on the rolling strain. The ultimate tensile strength of the rolled foils is 867-934 MPa and the electrical con ductivity is 19-40% of the pure copper conductivity. It is shown that annealing at 550°C results in an increase in the conductivity from 40 to 60% at a retained strength (microhardness) of the alloy.
Microstructure and properties of nanofilament Cu-Nb and Cu-Ag composites
The new high strength high electrical conductivity materials are demanded for advanced electric applications. Among them Cu-Ag and Cu-Nb wires are promising materials for generators of strong and variable magnetic fields production. Review of selected results of the studies into Cu-Ag and Cu-Nb based composite materials shows presence of various, not always well explained, mechanisms and phenomena which are observed during their production, examination and applications. Two classical copper alloys (with silver and with niobium) were selected for the investigations. The third material used in the studies was produced by bundle drawing of niobium wire in copper tube without classical melting and casting. Microstructure, mechanical and electrical properties were presented in relation to processing technology.
Mechanical behaviour of copper 15% volume niobium microcomposite wires
Materials Research, 2001
Cu-Nb microcomposites are attractive in magnet pulsed field technology applications due to their anomalous mechanism of mechanical strength and high electrical conductivity. In this sense, recently it was conceived the use of Cu 15% vol. Nb wires to operate as a high tensile strength cable for a diamond cutting tool (diamond wires) for marble and granite slabbing. The multifilamentary Cu 15% vol. Nb composite was obtained using a new processing route, starting with niobium bars bundled into copper tubes, without arc melting. Cold working techniques, such as swaging and wire drawing, combined with heat treatments such as sintering and annealing, and tube restacking were employed. The tensile property of the composite was measured as a function of the niobium filaments dimensions and morphology into the copper matrix, in the several processing steps. An ultimate tensile strength (UTS) of 960 MPa was obtained for an areal reduction (R = Ao/A, with Ao-initial cross section area, and A-final cross section area) of 4x10 8 X, in which the niobium filaments reached thickness less than 20 nm. The anomalous mechanical strength increase is attributed to the fact that the niobium filaments acts as a barrier to copper dislocations. Figure 6. Stress versus strain curve for the Cu 15 vol.% Nb composite.
Acta mater. Vol. 47, No. 5, pp. 1627-1634, 1999
A Cu-8.2 wt% Ag-4 wt% Nb in situ metal matrix composite was manufactured by inductive melting, casting, swaging, and wire drawing. The final wire ( ln A0=A 10:5, A: wire cross section) had a strength of 1840 MPa and 46% of the conductivity of pure Cu. The electrical resistivity of the composite wires was experimentally investigated as a function of wire strain and temperature. The microstructure was examined by means of optical and electron microscopy. The observed decrease in conductivity with increasing wire strain is interpreted in terms of inelastic electron scattering at internal phase boundaries. The experimental data are in very good accord with the predictions of an analytical size effect model which takes into account the development of the filament spacing as a function of wire strain and the mean free path of the conduction electrons as a function of temperature. The experimentally obtained and calculated resistivity data are compared to those of the pure constituents.
Microstructures and tensile behavior of carbon nanotube reinforced Cu matrix nanocomposites
Materials Science and Engineering: A, 2006
Carbon nanotubes (CNTs) have been considered as an ideal reinforcement to improve the mechanical performance of monolithic materials. However, the CNT/metal nanocomposites have shown lower strength than expected. In this study, the CNT reinforced Cu matrix nanocomposites were fabricated by spark plasma sintering (SPS) of high energy ball-milled nano-sized Cu powders with multi-wall CNTs, and followed by cold rolling process. The microstructure of CNT/Cu nanocomposites consists of two regions including CNT/Cu composite region, where most CNTs are distributed, and CNT free Cu matrix region. The stress-strain curves of CNT/Cu nanocomposites show a two-step yielding behavior, which is caused from the microstructural characteristics consisting of two regions and the load transfer between these regions. The CNT/Cu nanocomposites show a tensile strength of 281 MPa, which is approximately 1.6 times higher than that of monolithic Cu. It is confirmed that the key issue to enhance the strength of CNT/metal nanocomposite is homogeneous distribution of CNTs.
Processing, microstructure, and properties of ternary high-strength Cu–Cr–Ag in situ composites
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2000
A new class of ternary in situ metal matrix composites (MMCs) with high strength and high electrical conductivity consisting of heavily co-deformed Cu, Cr, and Ag is introduced. Three alloys are investigated in detail, namely, Cu–10wt.%Cr–3wt.%Ag, Cu–10wt.%Cr–1wt.%Ag, and Cu–4.5wt.%Cr–3wt.%Ag. The alloys were produced by inductive melting and chill casting. Because Cu–Cr and Cu–Cr–Ag alloys with hypereutectic Cr content are less ductile than previously investigated Cu–Nb, Cu–Ag, and Cu–Nb–Ag alloys, special attention was placed on optimizing microstructure with respect to both strength and ductility using thermal and thermo-mechanical processing schemes. These included various combinations of swaging, heavy wire deformation (using different lubricants), solution annealing at different temperatures followed by quenching, and aging at different temperatures. Optimized processing allows one to attain maximum wire strains of η=8.48 (η=ln(A0/A), A: wire cross-section). The wires have very high strength (for instance Cu–10wt.%Cr–3wt.%Ag: 1260 MPa at a strain of η=8.48) and good electrical conductivity (62% of the conductivity of pure Cu (IACS) at a strain of η=2.5 after solution treatment). Up to wire strains of η≈8.5 the strength is equal to that of Cu–20wt.%Nb. The wire strength is much higher than predicted by the linear rule of mixtures. The investigation presents the evolution of microstructure during the various thermo-mechanical treatments and relates the results to the observed mechanical and electrical properties. The strength is discussed in terms of Hall–Petch-type hardening.