Evaluation of ion-irradiation hardening of tungsten single crystals by nanoindentation technique considering material pile-up effect

Abstract

Ion-irradiation hardening of pure tungsten (W) single crystal was evaluated by nanoindentation (NI) technique considering material pile-up effect. Pure W single crystals of (001) surface orientation were ion-irradiated with 6.4 MeV Fe3+ to 0.1 dpa, 1 dpa or 2 dpa at 573 K. The irradiation hardening was evaluated by means of NI measurements with elastic-modulus-based correction (EMC) method [C. Heintze et al.: J. Nucl. Mater. 472 (2016) 196-205]. The effect of material pile-up in tungsten was so significant that the bulk equivalent hardness values by EMC method were about 70% and 85% of uncorrected results for irradiated and unirradiated W(001), respectively. The ion-irradiation hardening values by EMC based method were approximately 40%, 50% and 60% of uncorrected results for 0.1 dpa, 1 dpa and 2 dpa, respectively. The measured maximum pile-up height was higher for irradiated W(001) than for unirradiated W(001) at each indentation depth. An averaged pile-up height that was associated with the actual area of contact of pile up obtained from EMC hardness showed different responses to ion-irradiation depending on the indentation depth.