Abstract Nanoimprinting is a versatile technique for robust surface patterning on metallic materials at both micro- and nanoscales. While grain size is known to affect topography transfer during confined plastic flow, the underlying mechanisms remain unclear. To investigate this, nanoimprinting was conducted on nanocrystalline CuZn30, processed via High Pressure Torsion, and cold-worked CuZn30 using a diamond punch with a cavity height-to-width ratio of 2. High-resolution Transmission Electron Microscopy and Automated Crystal Orientation Mapping were used to analyze the plastic deformation mechanisms beneath and around the imprinted cavities. The tool topography is transferred to both materials as long as the grain size or subgrain size is smaller than the cavity width. Cold-worked CuZn30 shows localized stacking fault formation, twinning, subgrain fragmentation, and dislocation cell formation, particularly around larger cavities, whereas grain rotation and boundary-mediated plasticity dominate in the nanocrystalline samples. Notably, nanocrystalline CuZn30 achieves homogeneous plastic flow due to smaller grain size and absence of work hardening. These results demonstrate that a nanocrystalline microstructure is not strictly required for effective nanoimprinting. Rather, a cavity-width-to-(sub)grain-size ratio greater than one is crucial for sufficient plastic accommodation. The findings provide mechanistic insights into confined plastic deformation and underlying mechanisms at the sub-micron scale.
Frohnapfel et al. (Tue,) studied this question.