Microstructure and properties of nanofilament Cu-Nb and Cu-Ag composites (original) (raw)
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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...
Supercond. Sci. Technol. 19 (2006) 1233–1239
We report on the influence of the microstructure on the AC and DC magnetic properties of Cu–3.5% Nb nanofilamentary wires. Samples obtained from a single Cu–3.5% Nb wire were subsequently submitted to different plastic strain levels via drawing so that their microstructure was altered. Noticeable differences are observed in their isothermal DC magnetization curves that present a double-peak structure. The first peak, which occurs at low magnetic fields, is attributed to superconductivity induced in the Cu matrix due to the proximity effect. It is argued that the second peak is related exclusively to niobium. The dependence of these two distinct peaks on the characteristic nanometre length scales of the samples, i.e. dimension of the Nb filaments and interfilamentary spacing, are discussed.
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.
IEEE Transactions on Applied Superconductivity, 2014
The anomalous increase of the mechanical strength in copper matrix FCC-BCC composite materials caused by the specific nanoscaled microstructure formed by the heavy plastic deformation is associated mainly with the nature of the interface boundary areas. The differences in the nature of the interface areas in the Cu-Nb, Cu-V, and Cu-Fe have been discussed in connection with the parameters of crystallographic structure of three BCC elements (Nb, V, Fe). The nanostructured Cu-Nb, Cu-V, and Cu-Fe experimental high strength, high conductivity wires have been fabricated by the similar technological routes. The tensile strength and electrical conductivity for Cu-Nb, Cu-V, and Cu-Fe microcomposite wires are presented. The stability of the filamentary nanoscaled microstructure created by the large plastic deformation is investigated. We demonstrate that it is possible to maintain mechanical strength higher than 400 MPa after long time heat treatment between 250 • C and 400 • C.
FIM and 3D atom probe analysis of Cu/Nb nanocomposite wires
Nanostructured Materials, 1999
Two kinds of Cu/Nb nanocomposite wires were investigated using field ion microscopy (FIM) and 3D atom probe. These two techniques revealed for the first time the nanoscale microstructure of nanocomposite wire cross sections. FIM investigations confirmed the Cu and Nb texture and the disorientation between (111) Cu and (110) Nb planes. Low angle Nb/Nb grain boudaries were also observed. Thanks to 3D atom probe, parts of niobium fibres and copper channels a few nanometer width were mapped out in 3D. Smooth Cu/Nb interfaces were attributed to stress-induced diffusion. Shear bands, observed perpendicular to the wire axis, were attributed to tracks of moving dislocations in a copper channel.
Z. Metallkde. 86 (1995) 6
Fiber or ribbon reinforced in situ metal matrix composites (MMCs) consisting ofCu and 20 mass% Nb were produced by large strain wire drawing and cold rolling of a cast ingot. The microstructure of the composites was studied by use of scanning and transmission electron microscopy. The normal and superconducting properties of the wires and sheets in the presence of externally imposed magnetic fields were investigated and compared with the electromagnetic properties of pure Cu and Nb. The observations are discussed in terms of the microstructural changes during wire drawing and rolling. The current results substantiate that the . amount of internal phase boundaries and the filament spacing have considerable influence on the normal and superconducting properties of Cu-20 mass% Nb. On the basis of the current findings potential industrial applications are discussed .
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 ®nal 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 bound- aries. 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.