Microstructural stability of Cu–Nb microcomposite wires fabricated by the bundling and drawing process

The microstructural stability of Cu–Nb microcomposite wires fabricated by the bundling and drawing process was examined using TEM (Transmission Electron Microscopy). No flaws were observed near the interface regions between the bundled wires and the copper can, suggesting excellent bonding. Nb filaments were randomly distributed throughout the copper matrix and appeared straight or slightly curved in the bundled wires. The absence of heavily kinked filaments in the bundled wires is attributed to the break-up and cylinderization of niobium filaments during the bundling process. Niobium filaments were dissolved and numerous niobium precipitates formed in the copper matrix during high temperature bundling process. Twin bands were observed in the Cu–Nb, with the Nb filaments acting as barriers to twin propagation. Occasionally, the copper matrix on either side of the Nb filaments was found to have different texture components, which is thought to result from the reorientation of [111] into near [200] by twinning.