Enabling in situ cyclic microcantilever bending under electrochemical hydrogen charging with a FIB-fabricated multifunctional probe

Hydrogen-modified deformation must be investigated at the length scale of the defects governing plasticity, but rapid hydrogen effusion from small material volumes complicates micromechanical testing after electrochemical charging. This work presents a modular experimental concept that combines hydrogen-sensitive strain rate jump nanoindentation with cyclic microcantilever bending during active electrochemical charging. Strain rate jump tests on back-side hydrogen-charged single-crystal nickel (sx-Ni) and nanocrystalline nickel (nx-Ni) were used as a quantitative benchmark. The measured strain rate sensitivities agreed with literature values in the uncharged state and increased after hydrogen charging, from approximately 0.006-0.009 to 0.025-0.026 for sx-Ni and from 0.017–0.018 to 0.022–0.031 for nx-Ni. For cyclic bending, a three-electrode cell was combined with a FIB-fabricated multifunctional microbending probe. The probe preserves tip-to-optics calibration, enables scanning-probe imaging and alignment in electrolyte, and allows a microcantilever to be engaged and cyclically loaded at negative force ratios using the scratch-testing mode of a stand-alone nanoindenter. Stable load-reversal cycles were obtained during continuous electrolyte exposure and active hydrogen charging, demonstrating the mechanical and electrochemical functionality of the setup. The results establish a new complementary methodology for probing monotonic rate-dependent plasticity and cyclic deformation at the micrometre scale under hydrogen-charging conditions. The approach provides a basis for future quantitative studies of hydrogen-assisted cyclic plasticity and damage evolution in confined material volumes.