Constructing superhydrophobic micro/nano-hierarchical surfaces is an efficient means of reducing hydrodynamic drag on underwater vehicles. Titanium alloys, owing to their high strength and corrosion drag, have become essential structural materials for such applications. However, most existing surface-structuring approaches for titanium alloys rely on a single fabrication technique. This limitation constrains further improvements in drag-reduction performance. To address this challenge, this study proposes a multi-process composite fabrication approach that integrates the advantages of three complementary techniques to produce micro/nano‐structured superhydrophobic titanium alloy surfaces. Phase-controlled vibration micro-texturing (PVMT) is first applied to generate microscale pillar structures; ultrafast laser nano-texturing (ULNT) is then used to machining nanoscale structures; finally, surface energy modification (EM) is conducted through fluorination treatment. The PVMT technique is newly proposed in this work. By precisely controlling the phase difference between two cutting passes, the material removal behavior is regulated such that the residual material forms discrete micropillar arrays, which is favorable for enhancing drag-reduction performance. To verify the performance of this hybrid approach, titanium alloy samples were prepared under various process parameters, followed by wettability characterization and underwater drag measurements using a custom-built testing platform. Wettability results show that PVMT significantly improves hydrophobicity, increasing the static contact angle from 78.6° to 112.4°. When combining PVMT&ULNT&EM, the contact angle rises to 154.2°, demonstrating superhydrophobic behavior. Drag tests reveal that PVMT generated micropillar structures can reduce drag by up to 12.6%. With additional ULNT and EM treatments, the drag-reduction rate increases to a maximum of 22.1%, among the highest drag-reduction values reported for titanium alloy surfaces. Additionally, the surface drag reduction performance is recoverable. These experimental results confirm the efficiency of PVMT in constructing functional micropillar arrays, and validate the effectiveness of the PVMT&ULNT&EM composite process in fabricating hierarchical superhydrophobic surfaces for enhanced underwater drag reduction. This approach offers a promising route for functionalizing advanced underwater engineering materials.

Convex structures are a crucial type of surface functional structure whose shape significantly affects their performance. Tip-based machining and vibration texturing are two groups of state-of-the-art subtractive fabrication methods for micro/nano structures, each offering distinct advantages: tip-based machining excels in achieving small feature sizes, whereas vibration texturing improves production efficiency. This study aims to combine these methods to create a more powerful micromachining technique, namely tip-based vibration carving (TVC), particularly suited for fabricating shape-customized convex microstructures. In TVC, the vibration trajectory and nominal carving motion of the tip tool are parallel to the workpiece surface. In each vibration cycle, the tip tool removes some material while the remaining material becomes one convex microstructure. Therefore, the shape of convex microstructures can be customized by the design of vibration trajectories. By adopting high-frequency vibration, the production rate of convex microstructures can be highly efficient. Based on the fundamental principle of TVC, three types of TVC methods—sine-shape, O-shape, and U-shape TVC—are proposed, each employing distinct vibration trajectories. A prediction model for surface generation of convex microstructures is established based on the fusion of process mechanism and experimental data. Finite element simulations are conducted to analyze the material removal and deformation processes during TVC processing. Surface texturing tests are performed on the aluminum workpieces to verify the efficacy of the proposed TVC in producing various shapes and hybrids of convex microstructures. The experimental results also validate the accuracy of the developed prediction model of the surface morphology of generated microstructures. In addition, the feasibility of TVC on various materials, tool wear after processing, subsurface change of carving, and surface wettability are investigated.

Texturing micro-dimensional structures on silicon carbide particle-reinforced aluminum matrix (SiC_p/Al) composites is a promising technique for enhancing their tribological performance. However, owing to their heterogeneous material properties, the fabrication of high-quality microdimples on SiC_p/Al composites via methods such as laser texturing is challenging. This study introduces elliptical vibration texturing (EVT) to fabricate high-quality microdimples on SiC_p/Al through controlled material removal. A kinematic model was developed to predict dimple geometries, and the experimental results revealed that EVT can effectively create uniform microdimple textures with minimal surface damage. The process involves a transition between ductile and brittle‒ductile mixed removal modes, which promotes surface integrity. Tribological tests demonstrated that, compared with untextured surfaces, textured surfaces achieved a 40% reduction in the friction coefficient under lubricated conditions. Deeper dimple textures (6 μm) exhibited superior performance under higher loads owing to enhanced lubricant retention. This study presented a practical approach for improving the tribological performance of metal matrix composites for aerospace applications.

High-aspect-ratio metallic surface microstructures are increasingly demanded in breakthrough applications, such as high-performance heat transfer enhancement and surface plasmon devices. However, the fast and cost-effective fabrication of high-aspect-ratio microstructures on metallic surfaces remains challenging for existing techniques. This study proposes a novel cutting-based process, namely elliptical vibration chiseling (EV-chiseling), for the high-efficiency texturing of surface microstructures with an ultrahigh aspect ratio. Unlike conventional cutting, EV-chiseling superimposes a microscale EV on a backward-moving tool. The tool chisels into the material in each vibration cycle to generate an upright chip with a high aspect ratio through material deformation. Thanks to the tool's backward movement, the chip is left on the material surface to form a microstructure rather than falling off. Since one microstructure is generated in one vibration cycle, the process can be highly efficient using ultrafast (>1 kHz) tool vibration. A finite element analysis model is established to explore the process mechanics of EV-chiseling. Next, a mechanistic model of the microstructured surface generation is developed to describe the microstructures' aspect ratio dependency on the process parameters. Then, surface texturing tests are performed on copper to verify the efficacy of EV-chiseling. Uniformed micro ribs with a spacing of 1–10 μm and an aspect ratio of 2–5 have been successfully textured on copper. Compared with the conventional EV-cutting that uses a forward-moving tool, EV-chiseling can improve the aspect ratio of textured microstructure by up to 40 times. The experimental results also verify the accuracy of the developed surface generation model of microstructures. Finally,the effects of elliptical trajectory, depth of cut, tool shape, and tool edge radius on the surface generation of micro ribs have been discussed.