Effects of helium bubbles on deformation of aluminum matrix

Helium bubble influence on the deformation of aluminum is investigated via simultaneous electron backscatter diffraction and digital image correlation (DIC) during in situ tensile and compressive tests. The majority of helium is generated through the transmutation reaction ¹⁰B(n, ${\alpha )}^7$Li under neutron irradiation, which is carried out at 40 ${}^{\circ }$C to $\sim$0.3 dpa. The mesoscale deformation behaviors of aluminum matrix with and without helium bubbles are compared, and the interactions between helium bubbles and slip bands are analyzed. Helium bubbles along with other types of irradiation-induced defects (like dislocation loops and black dots) harden significantly the aluminum matrix around second-phase AlB${}_2$ particles. Slip bands cannot penetrate the areas with high-density irradiation-induced defects. They bypass such areas through cross slip, exhibiting slip band deflection. Transmission electron microscopy on irradiated materials after deformation reveals abundant helium bubbles, dislocations, dislocation loops and black dots around AlB${}_2$ particles, due to complex interactions between irradiation-induced defects with dislocations. Helium bubbles together with other types of irradiation-induced defects have pinning effects on dislocations, and pressurized helium bubbles may also punch out dislocation loops. The multiscale analyses demonstrate the helium bubble-dominated hardening.