Mechanism and modeling of metallic microfins by shear-extrusion net-forming

• A novel mechanical approach is proposed for creating microfins on metals, utilizing synergistic tool-surface interactions at a rate of 18 mm 2 /s. • A theoretical model is developed to predict the characteristic dimensions and profiles of microfins, with experimental validation showing an error of less than 5%. • Finite element analysis provides valuable insights into the stress distribution and formation mechanism throughout the entire forming process. • The shear stress induced by plastic strain significantly refines the grain size within the fabricated microfins. Surface micro- and nano-structures on metallic materials have a profound impact on the functionality of high-performance devices in electronic, biomedical and tribological applications. However, existing fabrication strategies for these metallic structures, including surface microfins, pose significant challenges due to inefficiency and procedural complexity, which hinder their scalability for industrial production. This study proposes a novel shear-extrusion net-forming strategy for fabricating surface microfins on metallic substrates. The strategy utilizes synergistic interactions between the tool and the material surface to enable the rapid extrusion-based formation of metallic microstructures at a rate of 18 mm 2 /s, while avoiding any material loss during processing. A predictive model developed within this framework achieves dimensional accuracy with an average error below 5 %. Finite element analysis reveals that localized stress distributions govern bending behavior and residual stress profiles, influencing both geometry and structural integrity. The microfin formation mechanism is driven by severe plastic deformation, with shear-induced grain refinement accelerating fin formation and improving surface hardness by ∼20 %. This work provides a scalable and industrially adaptable fabrication strategy for metallic microstructures and expands their potential industrial applicability in areas such as thermal management, catalysis and tribology.