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 low-dose 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