Experimental Investigation and Simulation of the Normal Conducting Properties of a Heavily Cold Rolled Cu-20 Mass%Nb in situ Composite (original) (raw)
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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 Metallurgica Et Materialia, 1995
Fibre or ribbon reinforcedin situ metal matrix composites (MMCs) consisting of Cu and 20 wt% Nb were produced by large strain wire drawing. The microstructure of the composites was investigated by means of optical and electron microscopy. The normal and superconducting properties of the MMC wires in the presence of external magnetic fields were examined and compared to the electromagnetic properties of pure Cu wires. The findings are discussed on the basis of the microstructural changes during deformation. The current results substantiate that the amount of internal boundaries and the filament spacing have considerable influence on the normal and superconducting properties of Cu-20% Nb.Faserversta¨rktein situ Verbundwerkstoffe mit metallischer Matrix (MMCs) aus Cu und 20 gew.% Nb wurden durch hohe Drahtverformung hergestellt. Die Mikrostruktur der Verbundwerkstoffproben wurde mit Hilfe licht- und elektronenoptischer Mikroskopie untersucht. Die normal- und supraleitenden Eigenschaften der MMC-Dra¨hte wurden unter dem Einflußa¨ußerer magnetischer Felder gemessen und mit den elektromagnetischen Eigenschaften reiner Cu-Dra¨hte verglichen. Die ermittelten Daten werden auf der Basis der mikrostrukturellen Entwicklung im Verlauf der Verformung diskutiert. Die vorliegenden Ergebnisse belegen, daß der Anteil an inneren Grenzfla¨chen und der Faserabstand einen betra¨chtlichen Einfluß auf die normal- und supraleitenden Eigenschaften von Cu-20% Nb haben.
Zeitschrift für Metallkunde 86 ( 1995)
Fiber reinfo rced in si tu metal matrix composites (MMCs) consisting of Cu :md 20 mass"!.. Nb were fabrica ted by liuge strain cold ro ll ing and wire drawing of a cast ingo!. The microstructural evolution of the composites was invcstigat,,"< 1 by me:ms of scanning and transmission electron microscopy. The mechanical properties of the MMCs were discussed on the basis o fthc microstructu ra l changes during deform:lIion. The results substantiate that the vol ume density of in ternal bou ndaries and the filament spacing have considerable innuence on the strength of Cu·20 mass% Nb. The evolution of the strength during defo rmation was simula ted by appl ica tion of analytical approHchcs which incorporate ex perimental data. The results revea l a very good corresponde nce to the behavior observed. On the basis of the curren t findings potentia l industrial applications a rc d iscussed.
Observation of amorphous areas in a heavily cold rolled Cu-20 wt% Nb composite
Materials Letters, 1995
A Cu-based metal matrix composite containing 20 wt% Nb was cast and heavily deformed by large strain cold rolling. During deformation, the initial Nb dendrites form into elongated filaments. The substructure of single Nb fibers was investigated by use of TEM, EDX and SAD. In heavily rolled specimens (ϵ= 99.4%), elongated dislocation cells as well as randomly arranged dislocations were observed. Furthermore, numerous amorphous areas were discovered within the Nb. Some of these non-crystalline areas extended over the ...
Correlation of superconductivity and microstructure in an in-situ formed Cu20%Nb composite
Physica Status Solidi (a), 1994
The normal and superconducting properties of a wire-drawn Cu–20%Nb alloy, forming a fibre reinforced in-situ composite, are investigated. The results are correlated to microstructural attributes of the composite and compared to findings in analogously processed pure Cu. The microstructure of Cu–20%Nb is characterized by the curled and elongated morphology of the superconducting Nb ribbons which are embedded in the Cu matrix. Whereas superconductivity in the heavily deformed composite is accomplished by the Nb filaments, the normal conducting properties which are determined by the Cu phase are considerably influenced by the Nb filament spacings. Only a slight dependence of superconductivity on the enhancement of the density of internal boundaries due to different degrees of deformation was observed.Die normal- und supraleitenden Eigenschaften einer drahtgezogenen Cu–20%Nb-Legierung, die sich zu einem faserverstärkten Verbundwerkstoff ausformt, werden untersucht. Die Ergebnisse werden mit den mikrostrukturellen Merkmalen des Verbundwerkstoffes korreliert und mit Resultaten von entsprechend verformtem reinem Cu verglichen. Die Mikrostruktur in Cu–20%Nb wird durch die gekrümmten und langausgezogenen Nb-Filamente, die in der Cu-Matrix eingebettet sind, charakterisiert. Während die Supraleitung in dem hochverformten Verbundwerkstoff über die Nb-Filamente entsteht, werden die normalleitenden Eigenschaften, die durch die Cu-Phase bestimmt werden, nachhaltig von den Nb-Faserabständen beeinflußt. Bei den unterschiedlich verformten Proben wird eine nur geringe Abhängigkeit der supraleitenden Eigenschaften von der Dichte der inneren Grenzflächen beobachtet.
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...
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.
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.