Neutron-scattering studies of an electron-irradiated 62Ni-- 41.4-at. %-65Cu alloy

Neutron-diffraction studies of the null matrix 62Ni-- 41.4-at. %-65Cu have been performed after thermal treatment and after irradiation with 3-MeV electrons at temperatures between 373 and 510 K. The diffuse neutron scattering has been measured to determine the Warren-Cowley short-range-order parameters and additionally the neutron small-angle scattering has been investigated for detecting any possible decomposition or segregation in the Ni-Cu alloy. In the special case of Ni-Cu alloys the experiments demonstrate the successful combination of electron-irradiation and neutron-diffraction measurement, two experimental procedures with normally contradictory requirements. As a result of the diffuse scattering a significant increase of the atomic short-range clustering under irradiation has been observed, corroborating the interpretation of previous electrical-resistivity and magnetic-susceptibility measurements. In small-angle scattering the formation of periodic concentration fluctuations is observed as it is expected for spinodal decomposition, giving the first experimental evidence of the suggested miscibility gap in Ni-Cu