Stability aspects of the high strength high conductivity microcomposite Cu-Nb wires properties

Extremely high strength in microcomposite Cu-Nb wires is associated with ultra-fine-scale microstructure. The extended interfaces between ribbon-like niobium filaments and copper matrix contain the areas of semi-coherent interfaces that are apparently the main reason of significant level of residual stresses observed in microcomposite Cu-Nb wires. The analysis of nonequilibrium of such microstructure has been done. The issue of stability of nanostructured two-phase Cu-Nb materials in the form of winding wires for pulsed magnets has been considered in the present work. The results of measurements of mechanical properties and electrical conductivity carried out on the same samples after periods of time up to 7 years are presented. Different types of Cu-Nb microcomposites with cross sections from 0.07 mm(2) to 21 mm(2) were investigated. It was shown that microcomposite Cu-Nb wires maintained essentially unchanged their mechanical and electrical properties after many years aging at room temperature. An analysis has been done on the correlation of the mechanical and conducting properties with microstructure.