Effects of neutron irradiation and post-irradiation annealing on pop-in crack propagation instabilities in 6061 aluminium alloy

• Mechanical tests are performed on Al-alloy subjected to irradiation and post- annealing Matrix hardening due causes the decrease of toughness properties Crack instabilities tearing modulus Fractography shows typically ductile fracture mechanisms after Fracture identical in any state: irradiated or not, heat-treated not This study analyses increase crack propagations (pop-in) with during testing aluminium alloy 6061 neutron irradiation. The aim is identify if propagation related microstructural heterogeneities, i.e. weak zones, they linked a competition between machine stiffness modulus. An in-depth mechanical instability analysis was comparing moduli materials. For this purpose an experimental program carried out hot cells facility at CEA Saclay conduct studies, Material Testing Reactor (mean conventional thermal fluence: 6.8 × 10 21 n th.conv .cm −2 ). material quantified using tensile heat treatments. effect measured by precracked CT12.5 samples. Damage were studied scanning electron microscope fractography classical micromechanisms found for all conditions without notable differences non evolution subsequent treatments therefore attributed matrix hardening/softening its nucleation voids brittle second phase particles. To investigate experimentally moduli, applied that softened material. It shown softening, number decreased eventually pop-ins disappeared. criteria J-Δa R-curves it concluded resulted from interaction stiffness. test results present compared those literature show very good agreement.