Microstructural change in AlMg3 alloy irradiated by spallation neutrons and high energy protons

An aluminum alloy Al–2.7wt%Mg (AlMg3) has been used as the material for the safety-hull of the Swiss Spallation Neutron Source (SINQ) target. In the present work, the microstructure in the unirradiated and that from the beam window of the safety-hull has been investigated. For irradiated material, samples with two different doses (0.7 and 3.6 dpa) were investigated. In unirradiated material the dislocation density is not high, and are mainly located near precipitates. The sizes of the precipitates range from 10 to 200 nm in grain interior. Larger precipitates over 500 nm locate mainly along grain boundaries. After irradiation at around 60 °C, high density of small dislocation loops and helium bubbles were introduced. The bubbles distribute homogeneously inside grains at 0.7 dpa. At 3.6 dpa the size distribution shows a bimodal behavior. The bubbles at grain boundaries are larger than those in grain interior. The precipitates are partially amorphized after irradiation.