The effects of neutron irradiation upon samples which had been pre-exposed at 300K, to thermal fluences of up to 8 x 1022/cm2 and fast fluences of up to 4 x 1022/cm2, were monitored by means of mechanical spectroscopy. The internal friction and dynamic shear modulus spectra, as a function of temperature, exhibited variations which were strongly dependent upon the dose. The 480K internal friction peak of the unirradiated alloy (previously attributed to solute dragging by dislocations) shifted to higher temperatures after irradiation. This peak-shift was interpreted in terms of dislocation pinning by irradiation-produced clusters. The shear modulus increased by 15% at low doses and remained stable during thermal cycling at 300 to 550K. It was shown that this hardening could not be explained by dislocation pinning alone. An additional direct bulk effect of interstitials and clusters, created by thermal neutrons, was proposed in order to account for it. Complete recovery of the shear modulus was observed for higher doses after thermal cycling.

Dislocation Pinning in a Low-Dose Neutron-Irradiated Al-Mg-Si Industrial Alloy. E.Carreño-Morelli, A.A.Ghilarducci, S.E.Urreta: Philosophical Magazine A, 1999, 79[2], 293-304