Influence of He ion irradiation on the microstructure and hardness of Ni–TiCNP composites

In the present study, samples of a titanium carbide nanoparticle-reinforced nickel alloy (Ni–TiC NP composite) were irradiated with 1 MeV He ions at 700 °C. The evolution of He bubbles and nanohardness was characterized using transmission electron microscopy (TEM) and nanoindentation, respectively. TEM images showed that the size and number density of He bubbles in the grains were affected by the He ion fluence. The number density first increased significantly and then decreased with increasing ion dose, while the size exhibited an inverse trend. Moreover, the swelling induced by He bubbles continuously increased with increasing ion dose. He bubbles also formed in the grain boundaries, interior of the TiC nanoparticles, and interfaces between the TiC nanoparticles and Ni matrix. Nanoindentation measurements indicated a decrease in nanohardness after irradiation, which is attributed to the disappearance of intrinsic dislocation lines caused by He ion irradiation.