Dose rate effect on micro-structure and hardness of Hastelloy-N irradiated by Xe ions

Abstract

Hastelloy-N alloys were irradiated by Xe+ with energies of 7 and 2 MeV at room temperature in order to investigate the effects of dose and dose rate on the change of micro-structure and nanohardness. Hardness was measured by nanoindentation, and micro-structure evolution and irradiation defects were identified by transmission electron microscopy (TEM) and positron annihilation coincidence Doppler broadening (CDB), respectively. The nanoindentation results showed that the hardness of alloys increased after irradiation, especially at a lower dose rate. At higher dose rate, TEM results indicated that irradiation defects were observed at first in this experiment, and the size of the defects increased, while their number density decreased as the dose increased. However, for a same total dose, the defects formed at a lower dose rate were larger, and their number density was also higher than that at a higher dose rate. Meanwhile, CDB analysis verified the growth of vacancy-type defects with increasing dose.