Vacancy like defects and hardening of tungsten under irradiation with He ions at 800 °C

The irradiation induced hardening and vacancy like defects are investigated as a function of irradiation fluences with 200 keV He ion implantation at 800 °C in this work. Nano-indentation tests show the irradiation induces hardening and the hardness values increase with increasing irradiation fluences. Doppler broadening spectroscopy analyses of slow positron annihilation find that a large amount of vacancy like defects are produced under irradiation. When the He/dpa ratio is less than about 2.2% He/dpa, the vacancy like defects include mainly empty vacancy clusters and loops, and HenVm complexes. When the He/dpa ratio is more than about 2.2% He/dpa, the vacancy like defects become mainly HenVm complexes with increasing irradiation fluences. Meanwhile, these complexes increase in size and He/V ratio while the irradiation fluences increase. Based on the Orowan hardening mechanism, we discuss the relationship between irradiation induced hardening and defects under indentation, especially the contribution of HenVm complexes to the hardening.