Strength and electrical conductivity of a deformation-processed Cu-5 Pct Nb composite
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I.
INTRODUCTION
DEFORMATION-induced metal-metal composites containing Cu as the matrix phase and an insoluble metal, such as Nb, as the filamentary phase possesses both high strength and good electrical and thermal conductivity. This combination of properties is an outstanding feature of Cu-Nb-type composites. Numerous previous studies have been reported on Cu-Nb composites containing between 10 and 30 vol pct Nb, showing the pronounced increases in strength obtained with increasing degrees of deformation processing by drawing [z,2,3j or rolling. ~4~ However, it has not been established if such strengthening still occurs in these composites when the amount of the filamentary phase is much less than 10 vol pct. While the strength of such composites is expected to be reduced, conductivity is expected to be increased, which could result in Cu-Nb composites with good strength/ conductivity properties. Extrapolations of strength values at larger Nb contents predict a maximum ultimate tensile stress of about 675 MPa for a composite with 5 vol pct Nb after deformation processing by drawing to a reduction of 99.999 pct, which is about one half of the strength for a 10 vol pct Nb composite, t3] Some limited earlier work on electrical resistivity of Cu-Nb composites showed that the electrical resistivity did decrease as the Nb content was decreased from 15 to 7.5 vol pct, as expected.J5,6] These results suggest that on a strength basis, deformation-processed Cu-Nb composites with Nb contents less than 10 vol pct are not likely to be of much interest, but on a strength/conductivity basis, they may still exhibit favorable properties. However, these conclusions on the strength and conductivity properties of W.A. SPITZIG, Senior Metallurgist, F.C. LAABS, Associate Chemist, E.D. GIBSON, Associate Metallurgist, and J.D. VERHOEVEN, Senior Meta/lurgist/Materials Science and Engineering Professor, are with Ames Laboratory, Iowa State University, Ames, IA 50011. H.L. DOWNING, Professor of Physics, is with Drake University, Des Moines, IA 50311. This article is based on a presentation made in the symposium "High Performance Copper-Base Materials" as part of the 1991 TMS Annual Meeting, February 17-21, 1991, New Orleans, LA, under the auspices of the TMS Structural Materials Committee. METALLURGICAL TRANSACTIONS A
deformation-processed Cu-Nb composites containing low Nb contents are based on limited data and extrapolations of these data. Therefore, to evaluate the decrease in strength that occurs in deformation-processed Cu-Nb alloys at Nb contents below 10 vol pct and to determine the strength/conductivity properties of these lower Nb content alloys, the mechanical properties and electrical conductivities were determined for a Cu-5 vol pct Nb composite deformation processed by drawing to reductions up to 99.9993 pct.
II.
MATERIALS AND PROCEDURES
An ingot of Cu-5 vol pct Nb was prepared by consumable arc melting an electrode containing strips of Nb into a water-cooled Cu m o l d y ] A double melting procedure was employed to promo
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