Impact of neutron irradiation on hardening of baseline and advanced tungsten grades and its link to initial microstructure

Six tungsten grades were irradiated in the Belgian material test reactor (BR2) and characterized by Vickers hardness tests in order to investigate the irradiation-induced hardening. These tungsten grades included: Plansee (Austria) ITER specification tungsten, ALMT (Japan) ITER specification tungsten, two products from KIT (Germany) produced by powder injection molding (PIM) and strengthened by 1% TiC and 2% Y2O3 dispersed particles, and rolled tungsten strengthened by 0.5% ZrC from ISSP (China). The materials were irradiated face-to-face at three temperatures equal to 600 degrees C, 1000 degrees C, and 1200 degrees C to the dose of similar to 1 dpa. The Vickers hardness tests under 200 gf (HV0.2) were performed at room temperature. The Vickers hardness increases as the irradiation temperature increases from 600 to 1000 degrees C for all materials, except for the ZrC-reinforced tungsten, for which the increase of hardness does not depend on irradiation temperature. The irradiation-induced hardness decreases after irradiation at 1200 degrees C. This is a result of defect annealing enhanced by thermally activated diffusion. However, even at 1200 degrees C, the impact of neutron irradiation on the hardness increase remains significant; the hardness increases by similar to 30 to 60% compared to the non-irradiated value. In the case of TiC-strengthened material, the irradiation hardening progressively raises with irradiation temperature, which cannot be explained by the accumulation of neutron irradiation defects solely.

Automated summary

Six tungsten grades were irradiated at different temperatures and doses to investigate the irradiation-induced hardening through Vickers hardness tests. Most materials showed an increase in Vickers hardness as the irradiation temperature increased from 600 to 1000 degrees Celsius, except for ZrC-reinforced tungsten. The hardening in TiC-strengthened material progressively increased with irradiation temperature, not solely explained by the accumulation of neutron irradiation defects.