The influence of the thermomechanical process on the behavior of 6xxx aluminum alloysunder ion irradiation

Aluminum alloys have been widely used in nuclear research reactors (NRRs) since the 1960s. This choice is easily explained by the high thermal conductivity, low gamma heating, low activation and high neutron transparency of the material under irradiation. Research reactors use 5xxx and 6xxx aluminum alloys for their core components because of better corrosion behavior and mechanical properties. While increasing the safe and efficient use of NRR, the manufacturing of such alloys can be challenging in terms of thermomechanical processing indeed the appropriate properties of such alloys are mainly induced by very specific thermal treatment, which usually consist of annealing, quenching and artificial ageing.Due to a wide use of such alloys in the automotive industry, the thermomechanical process and its influence on the mechanical properties is already well known and documented in the literature. However, one of the key differences between the automotive industry applications and those of NRRs is the thickness of the manufactured components. Indeed, most of the available research data is available for thin components while the nuclear industry is often opting for thicker ones. Due to this specificity, quenching has to be carefully monitored and understood to obtain a very homogeneous material.In this study, using a typical thermal processing sequence for 6xxx aluminum alloys but varying the quenching rate, we propose to monitor the microstructure formed in aluminum component prior to irradiation in NRRs. Then, irradiating the different tempers with ion beams, targeting various DPA rates and fluences, we examined the various responses of the materials and examined in particular the formation of the voids and cavities, in order to link the influence of the microstructure on the swelling induced by three-dimensional defects. Results picture a precipitate-dependent behavior in terms of swelling. Precipitate dissolution and amorphization with ion irradiation are observed. A numerical evaluation of swelling rates has been conducted using TEM observation on ion irradiated material. Using previous irradiation data from reactors and other ions irradiations, we try to monitor and evaluate the swelling of such material using the Brailsford and Bullough equation, which implies a swelling rate linked to the damage rate and the inherent material behavior.