Irradiation disordering and ordering of Cu3Au by fusion neutrons

Ordered and partially ordered Cu3Au alloys (S=0.30-0.99) have been irradiated at 4 K and 300 K with fusion neutrons at RTNS-II. The disordering rate was measured by monitoring electrical resistivity. The analysis of 4 K irradiations and a comparison with fission reactor irradiations indicated that the disordering rate depended upon the long-range order parameter, S. The disordering is defined by dS/dφt=-S(k1-k2S), where k1 and k2 are scaled with damage energy. The results of 300 K irradiation indicated that reordering competed significantly with disordering in the partially ordered sample. Compared to the results of 4 K irradiation, the net disordering rate at 300 K was higher than that at 4 K. This difference and the dependence of disordering rate on S is discussed in terms of the effect of disorder and thermal displacements on cascade cooling processes. (orig.)