Internal friction and point defects in ordered βCu-Zn and βCu-Zn-Al

Abstract
The internal friction and the torsion modulus have been measured in an inverted torsion pendulum using quenched beta Cu-Zn and beta Cu-Zn-Al alloys. Peaks observed at -50 degrees C for the B2 ordered alloys and at -15 degrees C for the DO3 ordered alloys have been associated with (111) nearest neighbour vacancy-Cu atom pairs. Peaks found at 100 degrees C and 200 degrees C have been interpreted as being due to next nearest neighbour Cu pairs on the Zn rich sublattice. From the results a vacancy formation energy of 52 kJ mol-1 is deduced. Comparisons with existing diffusion data are presented.