TABLE OF CONTENTS Heat-resistant copper alloys having high electrical and/or thermal conductivities are required in a variety of applications, including resistance welding electrode contacts, electrical switches, microwave and X-ray tube components, incandescent lamp lead wires and neutron irradiation targets [21].
The wrought Cu-Cr and Cu-Zr alloys commonly used for elevated temperature applications are strengthened through thermomechanical treatments, which cause precipitation and stabilization of a strain-hardened structure. In such alloys, phenomena such as recovery and recrystallization start taking place at a temperature of about 450 C. Using the MA technique, it has been possible to extend the amount of chromium in the copper matrix. The use of PCAs is avoided in order to have high electrical and thermal conductivity in the final material by minimising impurities. Cu-5% Cr powder could be prepared by MA of elemental powders. The MA powder was consolidated by hot extrusion. A strength level of 75 MPa could be achieved, which is attributed to fine grain structure and dispersion strengthening. Ductility of 8% and conductivity of 60% of the copper were found after the heat treatment [22,23].
Alumina dispersion-strengthened copper has been produced by MA of copper powder and an amorphous Al(OH) 3 powder [24]. The Al 2O 3 is created in situ in the copper matrix at 254 C during heating of the green compacts to the sintering temperatures. Consolidation of the MA powder was carried out by cold compaction followed by sintering at 940 C in a nitrogen atmosphere. The highest hardness (110 VHN)...
