A small-angle neutron scattering study of the effects of high-dose electron irradiation on the precipitates in an Al-11.8 at% Zn alloy

The effects of high-dose electron irradiation, 2 MeV electrons at a flux of 10¹⁴ electrons/cm² s, on the precipitates in an Al-11.8 at% Zn alloy are reported. The small-angle neutron scattering experiments were performed on unirradiated and irradiated samples under identical conditions. It is observed that under higher doses the precipitates behave differently as compared to lowdose irradiation. No initial large drop in the magnitude of scattering is seen in high-dose irradiation, rather a continued increase in scattering with a simultaneous increase in the precipitate size. It is believed that at low doses some precipitates dissolve in the matrix which then becomes supersaturated, and with enhanced rate of diffusion as a result of continued irradiation, the remaining precipitates grow rapidly. As the supersaturation reduces, a coarsening mechanism takes over, via a radiation-enhanced diffusion mechanism.