Structure of extruded and dravvn vvires of high-purity copper

Abstract

The structure of extruded wires of three grades of copper with purity higher than 99·7% has been studied. The structure is controlled directly by extrusion temperature and cooling velocity after the dynamic recrystallization of materials at the die outlet. It is possible to prevent both uniform and selective grain growth by secondary recrystallization, and grain coarsening by decreasing the extrusion temperature and intensive cooling of the extruded wire. The structure is not determined by grain orientations in the cast billets. It was found impossible to remove the non-uniformity of the extruded wire structure by recrystallization, even after drawing with a 40−50% reduction. A uniform recrystallized structure of highpurity copper is obtained only in wires drawn with a reduction greater than 80%. The lower extrusion temperature in the range 830°−880°C results in a more uniform structure after a lower degree of cold work, and thus in higher toughness expressed by elongation.