Hardening Mechanisms of “Cold” Rolled Tungsten after Neutron Irradiation: Indentation and Finite Elements Modelling

The mechanical properties of “cold” rolled tungsten sheet after neutron irradiation at high temperature are investigated by instrumented indentation and crystal plasticity finite element modelling (CPFEM). Neutron irradiation to a dose of 0.2 displacements per atom was performed in the temperature range from 600 to 1200 °C in the Belgian material test reactor BR2 at SCK CEN, Mol. The contribution of the irradiation damage in the constitutive laws has been deduced by utilizing the load-depth curves of the indentation measurements and incorporating microstructural information from transmission electron microscopy measurements. The simulated load-depth curves are in very good agreement with the experimental data indicating that the model can characterize the plastic deformation of the irradiated W material. It is found that the irradiation temperature has almost no effect on the load-depth curves and the hardness increase, of around 19% after irradiation, is temperature independent within errors. The formation of voids after irradiation is the main cause of irradiation induced hardening while the dislocation loops have a much lower influence. Indentation tests at low and high loading rates showed that the void dominated microstructure is more sensitive to the increase of the deformation rate.