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Tungsten is one of the most promising plasma-facing materials (PFMs) to be used in the nuclear fusion reactor as divertor material in the future. In this work, W2+-ions bombardment is used to simulate the neutron irradiation damage to commercial pure tungsten (W) and rolled tungsten–potassium (W–K). The 7 MeV of 3 × 1015 W2+-ions/cm2, 3 MeV of 4.5 × 1014 W2+, and 2 MeV of 3 × 1014 W2+-ions/cm2 are applied at 923 K in sequence to produce a uniform region of 100 nm–400 nm beneath the sample surface with the maximum damage value of 11.5 dpa. Nanoindentation is used to inspect the changes in hardness and elastic modulus after self-ion irradiation. Irradiation hardening occurred in both materials. The irradiation hardening of rolled W–K is affected by two factors: one is the absorption of vacancies and interstitial atoms by potassium bubbles, and the other is the interaction between potassium bubbles and dislocations. Under the condition of 11.5 dpa, the capability of defect absorption can reach a threshold. As a result, dislocations finally dominate the hardening of rolled W–K. Specific features of dislocation loops in W–K are further observed by transmission electron microscopy (TEM) to explain the hardening effect. This work might provide valuable enlightenment for W–K alloy as a promising plasma facing material candidate. [ABSTRACT FROM AUTHOR]

Tungsten–potassium (WK) alloy with ultrafine/fine grains and nano-K bubbles is fabricated through spark plasma sintering (SPS) and rolling process. In this study, 3-MeV W2+ ion irradiation with a tandem accelerator is adopted to simulate the displacement damage caused by neutrons. As the depth of irradiation damage layer is limited to only 500 nm, the hardening behaviors of WK alloy and ITER (International Thermonuclear Experimental Reactor)-W under several damage levels are investigated through Bercovich tip nanoindentation test and other morphological characterizations. The indenter size effect (ISE), soft substrate effect (SSE), and damage gradient effect (DGE) are found to influence the measurement of nano-hardness. Few or no pop-ins in irradiated samples are observed while visible pop-in events take place in unirradiated metals. Extensive pile-up with different morphology features around the indentation exists in both WK and ITER-W. The WK shows a smaller hardness increment than ITER-W under the same condition of displacement damage. This study provides beneficial information for WK alloy serving as a promising plasma facing materials (PFMs) candidate. [ABSTRACT FROM AUTHOR]