Bundling and drawing processing of Cu–Nb microcomposites with various Nb contents

Bundling and drawing processing was used to produce high strength large diameter Cu–Nb wires for magnet applications. The microstructure and mechanical properties of bundled heavily drawn Cu–Nb wires were examined. The strength increased gradually with increasing Nb content while the ductility was insensitive to Nb content. The ratios of yield stresses are found to be close to those of Young’s moduli in various Cu–Nb microcomposites, suggesting that the strength is primarily controlled by athermal obstacles. The fracture morphologies show ductile fractures irrespective of Nb contents. Secondary cracking along the interfaces between sub-elemental wires was occasionally observed and the frequency of secondary cracking increased with increasing Nb content. Secondary cracks due to debonding along the interface between sub-elemental wires were also observed to be more frequent at 295 K than at 75 K. The more frequent debonding at 295 K may be due to relatively large triaxial stress state caused by more localized necking of sub-elemental wires.