The Irradiation Effects on the Nanoindentation Hardness and Helium Bubbles Evolution Mechanism of Ni-based Alloy

High-dose neutron irradiation could produce various kinds of microstructural defects, and the radiation resis-tance of nickel alloy is put forward for higher requirements under the high temperature. To simulate the (n, alpha) reaction, helium ions with an energy of 540 keV were implanted into nickel-based alloy 617 at 700 degrees C. The microstructure and mechanical properties were established by comparing the nanoindentation hardness before and after irradiation. For the low dose irradiation, the microstrain induced by vacancy-type defects like He-vacancy clusters and helium bubbles is slight, which would not result in a large increase of hardness. The hardening effect of high-temperature irradiation was much lower than that of room-temperature irradiation due to the recovery of matrix defects. The actual distribution of helium bubbles observed by Transmission Electron Microscope (TEM) was comparable to the SRIM simulation result. The helium bubbles were spherical near the surface of the alloy and polyhedral deeper in the matrix. Moreover, chromium carbide had a strong trapping effect on helium bubbles. The shapes and distribution of the helium bubbles were analyzed to evaluate irradi-ation effects on nickel-based alloys.