Effect of temperature on surface modification and the trapping/re-emission behaviour of Al and an AlMgSi alloy during MeV energy He implantation and post-irradiation annealing

Irradiation at different temperatures by MeV energy 4He+ ions and post-irradiation annealing performed on Al and an AlMgSi alloy were studied by RBS (Rutherford Back Scattering), SEM and optical microscopy. For the applied temperatures (RT-825 K) and energies (0.6-3.5 MeV) blistering or exfoliation, but no porous structure has been observed on the implanted area. For all implantation energies, the peak He concentration corresponding to a critical dose for surface deformation is in strong correlation with the tensile strength of the target material. At RT it has a constant value (33 at% for Al and 48 at% for AlMgSi), independent of the bombarding energy. At elevated temperatures it decreases in accordance with the temperature dependence of tensile strength. During post-irradiation annealing the He is released in two stages. At the onset of blistering or exfoliation, the release is originated from the volume under the detaching layers; the second stage of release occurs at temperature around 780 K in both materials. (orig.)