Synergistic effects of hydrogen and helium on dislocation loop rafting phenomena and hardening behavior of chromium

Dislocation loop rafts (DLRs), which are ordered arrangements of dislocation loops, are commonly observed in metals under neutron and heavy ion irradiation, yet they have seldom been observed under light ion irradiation. In this study, we reported the formation of DLRs under the synergistic effects of hydrogen and helium in a pure chromium (Cr) coating. Irradiation at room temperature with either single H ⁺or He ⁺ did not result in the formation of DLRs within the Cr coating. Approximately half of the dislocation loops induced by single H ⁺ and He ⁺ irradiation were of the a ₀〈100〉 type. Nevertheless, DLRs appeared under the combinational irradiation of H ⁺and subsequent He ⁺. The rafts were densely distributed, with lengths of up to 150 nm, and were exclusively composed of 1/2 a ₀ [11–1] variants along the 〈110〉 crystallographic direction. The emergence of DLRs, affected by the synergistic effect of H and He, results in an enhancement of irradiation hardening.