Dynamics on Transitional Ordering Process in Cu₃Au Alloy from Disordered State to Ordered State

Abstract

The transitional process in the Cu 3 Au alloy from the disordered to the ordered state and the relaxation process in the phase change in Cu 3 Au have been investigated by measuring the time dependence of the X-ray superstructure line width and the electrical resistivity. The process is realized by a rapid change of the sample temperature in comparison with the relaxation time of this process. The average cluster size increases in proportion to t 1/2 irrespective of the ageing temperature. This is compared with the theoretical result of Kawasaki et al. The change of the distribution function of the size of the ordered clusters is obtained from the superstructure line shape. We observe two kinds of relaxation times τ D→0 and τ 0→D . τ D→0 from the disordered to the ordered state is comparatively long and shows a kind of the showing down phenomenon. In contrast to this, τ 0→D from the ordered to the disordered state does not show such slowing down near T t . By assuming an appropriate model, this relaxation phenomenon is explained.