Relaxation of Diffused Zinc Atoms During Short-Range-Ordering in Cu-30% Zn Alloy

Abstract

Abstract The internal friction which is a diffusion dependent physical property has been used as a means to determine the kinetics of short range order in (Cu-30% Zn) alloy. Curves of relative (Q~ l /Q0~ 1) against annealing time have been plotted for various annealing temperatures. An average activation energy of 1.7 eV was found for the ordering process, which is equal to the activation energy for zinc diffusion in coarse grained copper. When an alloy having short range order (SRO), is quenched from high temperatures, excess vacan-cies are liberated which will enhance diffusion, and hence the ordering rate during subsequent anneal-ing. Due to this enhanced ordering rate, the equi-librium degree of short range order canbe achieved in reasonable times even at rather low temperatures, provided that vacancies are mobile at these tempera-tures. For copper-zinc alloys in the alpha phase, the existence of SRO has been theoretically 1 establish-ed and experimentally demonstrated by many wor-kers (cf. CLAREBROUGH et al. 2). Evidence from diffuse X-ray and/or neutron scattering experiments is not available because of the small difference in scattering power of copper and zinc 3 atoms. Long range order in alpha brass above — 30 °C is im-probable 3 because of the rather low ordering en-ergy of the system.