論文 - 閻　紀旺

Micromachining of Carbon Fiber Reinforced Plastics Using Femtosecond Pulsed Laser

Konishi, Y; Yan, JW

NANOMANUFACTURING AND METROLOGY 8 （ 1 ）  2025年12月

ISSN  2520-811X

　概要を見る

Microscale grooves and holes were fabricated in carbon fiber reinforced plastics (CFRPs) using femtosecond pulsed laser irradiation, and the characteristics and mechanisms of laser processing were investigated. The relationship between laser fluence and ablation depth was established by measuring the cross-sectional profiles of the microgrooves produced at different laser fluences. Furthermore, the effect of the angle between the edge of the micro holes and the carbon fibers was examined by analyzing the edges and wall surfaces of circular and rectangular holes. Experimental results revealed that the laser processing mechanism was strongly dependent on fiber orientation due to significant heat conduction along carbon fibers. The findings of this study contribute to a deeper understanding of the ultrashort pulsed laser processing characteristics and mechanisms for creating small holes in CFRPs and emphasize the possibility of drilling high-precision holes that can be used in the direct bonding of sensors/IC chips to CFRPs.

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Effect of System Dynamics on Surface Topography in Fast Tool Servo-Based Diamond Turning of Microlens Arrays

Hashimoto T., Yan J.

Nanomanufacturing and Metrology 8 （ 1 ）  2025年12月

ISSN  2520811X

　概要を見る

A lens array is often used for optical components of sensing devices, requiring high surface quality and form accuracy. Fast tool servo (FTS)-based diamond turning is one of the technologies for manufacturing complicated shapes, such as freeform optics, structured surfaces, and microlens arrays, with high machining efficiency. In this study, lens array machining was performed on copper using an FTS on a diamond turning machine. For evaluating the lens array surface topography, the focus was on surface waviness formation. As a dominating factor of surface waviness, the system dynamics behavior was investigated by capturing and analyzing the position signal. It was found that a specific waviness pattern could be formed on the surface due to the servo response. By considering the dynamics of the FTS system from the captured signals, the FTS system behavior was identified, and optimal machining parameters for the lens array were proposed. A machining test under the optimized cutting conditions reduced the average Sdq used to quantify the waviness amount from 93 to 50 µrad and the standard deviation from 33 to 3 µrad, which greatly improved the consistency in accuracy for all lens arrays. This study will contribute to the appropriate utilization of FTS systems in the ultraprecision machining of various advanced optics, such as microlens arrays.

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Amorphization of pure aluminium in ultraprecision cutting process: experimental observation and theoretical analysis

He C., Wang S., Yan J.

CIRP Journal of Manufacturing Science and Technology 60   76 - 87 2025年09月

ISSN  17555817

　概要を見る

Preparing amorphous pure metals has long been significantly challenging because of their stringent transformation requirements. Here, we report a surprising discovery: the preparation of a layer of amorphous aluminium by ultraprecision cutting a polycrystalline bulk material. The findings indicated that under specific cutting conditions, polycrystalline aluminium was transformed into a completely amorphous phase on the surface layer. Additionally, the material matrix exhibited shear bands, including an amorphous phase, a 9 R phase, and high-density SFs. The modification resulted in a significant increase in surface micro-hardness, with the average value increasing from 0.93 ± 0.13 GPa to 2.21 ± 0.92 GPa. The amorphization in the ultraprecision cutting process is attributed to the high shear strain and strain rate, as confirmed by molecular dynamics simulation and theoretical calculation. This study provides a novel approach for preparing an amorphous layer on a crystalline aluminium bulk material to enhance its surface properties.

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Micro-convex structure-assisted laser-induced backside dry etching for high-efficiency fabrication of micro-groove array on fused silica toward manipulation of wetting characteristics

Huang H., An H., Qian Y., Zhang Z., Jiang M., Yan J.

Journal of Manufacturing Processes 145   236 - 251 2025年07月

ISSN  15266125

　概要を見る

Fused silica has garnered significant attention in various industrial applications. The creation of surface micro/nanostructures on fused silica can impart specialized functional properties, such as extreme wettability, ultra-high transmittance, and excellent antimicrobial characteristics. Nonetheless, existing technologies for achieving surface micro/nanopatterning of fused silica, including wire electrical discharge machining, chemical etching, and electrochemical deposition, generally suffer from long processing cycles and high energy consumption, which are inconsistent with the development concept of the low-carbon economy. In this study, a novel approach termed micro-convex structure-assisted laser-induced backside dry etching (MCSALIBDE) is proposed for high-efficiency fabrication of micro-groove array on fused silica surfaces. The synergistic effect of enhanced heat conduction and plasma explosion in a confined space facilitates material ablation. The impact of processing parameters including scanning pitch and peak laser power intensity on the morphological and topographical features of the MCSALIBDE-processed fused silica surfaces is studied. Notably, the micro-groove structures with a depth-to-width ratio of 1.19 is fabricated. Furthermore, the wetting behaviors of the MCSALIBDE-processed fused silica surfaces before and after annealing treatment are studied. Experimental findings reveal that the MCSALIBDE-processed fused silica surfaces exhibit enhanced hydrophilicity compared to the untreated one. After annealing treatment, a transformation from hydrophilicity to superhydrophobicity is observed. The superhydrophobic surfaces produced under different laser parameters exhibit distinct adhesion and droplet bouncing behaviors. This work offers an in-depth understanding of the high-efficiency fabrication of micro/nanostructures on fused silica surfaces and as well the modulation of their wetting characteristics, heralding innovations in surface engineering for diverse applications.

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Micro-amplitude vibration-assisted scratching: a new method for one step and controllable fabrication of the microscale V-groove and nanoscale ripples

Wu H., Huang H., Zhang Z., Yan J.

International Journal of Extreme Manufacturing 7 （ 3 ）  2025年06月

ISSN  26318644

　概要を見る

Highlights A micro-amplitude vibration-assisted scratching method was proposed. One step and controllable fabrication of microscale V-groove and nanoscale ripples was achieved. The effects of processing parameters on the resultant structures were explored. Relationships between processing parameters and dimensions of the resultant structures were established. Complex patterns were fabricated on flat and curved surfaces, achieving various structural colors.

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Unveiling the effects of laser scanning direction and processing parameters on heat transfer and ablation behavior of CFRP

An H., Qian Y., Jiang M., Huang H., Yan J.

Composites Part B: Engineering 298 2025年06月

ISSN  13598368

　概要を見る

Carbon fiber reinforced plastic (CFRP) has found extensive applications in aerospace, automotive, and biomedical fields owing to its exceptional mechanical properties. Nanosecond pulsed laser processing offers a promising avenue for treating CFRP laminates; however, the inevitable thermal damage during processing may significantly degrade the surface integrity. An in-depth analysis of the correlation between ablation characteristics of CFRP and laser processing conditions is essential for understanding the complex heat transfer and ablation mechanisms during laser processing of CFRP and is a prerequisite for improved control of thermal damage. This study examines the thermal transfer and ablation behavior of CFRP subjected to nanosecond laser ablation, focusing on how laser scanning direction and processing parameters influence the surface characteristics of the laser-ablated regions. The results indicate that the width of the heat-affected zone (HAZ) increases with increasing laser power, decreasing scanning speed, and decreasing scanning pitch. Moreover, the scanning direction plays a crucial role in determining the HAZ characteristics and material removal rate. Processing CFRP along the 0° direction relative to the carbon fiber orientation yields higher efficiency and less thermal damage compared to the 90° direction. Chemical composition analysis reveals that laser ablation induces a structural transformation in carbon fibers, shifting from sp2 graphite-like lattice orbitals to sp3 hybird orbitals. Numerical simulations further elucidate the heat transfer and ablation mechanisms under various experimental conditions. This study contributes to a deeper understanding of the laser-CFRP interaction, facilitating the development of high-integrity CFRP surfaces and broadening their practical applications across multiple industries.

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Investigation of the Effect of Tool Rotation Rate in EDM Drilling of Ultrafine Grain Tungsten Carbide Using Predictive Machine Learning

Journal of Manufacturing and Materials Processing 2025年06月

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Time delay compensation in high-speed diamond turning of freeform surface using independent fast tool servo with a long stroke

Hashimoto T., Yan J.

Precision Engineering 93   515 - 527 2025年05月

ISSN  01416359

　概要を見る

The demand for wearable device applications has continuously grown in recent years, especially with the significant rise of augmented and virtual reality technologies. Freeform optics plays a crucial role in these devices by enhancing optical performance, shortening the light path, and reducing the weight, all while allowing for smaller, lighter systems with higher efficiency. The independent fast tool servo (FTS)-based diamond-turning method stands out as a highly effective technique for fabricating freeform shapes with high accuracy and productivity. However, microsecond-order time delays occur within the system, significantly impacting form accuracy as machining speeds increase. This study explores the sources of form errors in freeform surface fabrication associated with the FTS diamond-turning process, with particular attention to the effects of clocking angle errors caused by the time delay. These errors were found to greatly affect form accuracy, especially at higher machining speeds. The FTS position data were analyzed, and time delays under various operational conditions due to servo control were confirmed. To precisely identify the extent of the time delay, a cylindrical surface was machined under high-speed conditions, and the clocking angle error was measured using a non-contact chromatic probe. Results showed that time delays originating from the machine platform had a significant effect on form accuracy. By accurately identifying and compensating for these time delays, the clocking angle error was eliminated. To validate the effectiveness of the time-delay compensation strategy, a cylindrical freeform surface was machined after the compensation, and the clocking angle error was minimized down to 0.00014° evaluated by on-machine measurement. The form accuracy of the freeform machining result after compensation was achieved at 0.85 μm PV. This study establishes a methodology for identifying and compensating for time delays in an independent FTS system, contributing to improved form accuracy in freeform optics fabrication.

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Evolution of surface and subsurface properties of Zr-4 alloy under the combined effects of laser heat treatment and laser gas nitriding: Microscopic morphology, chemical composition, and mechanical behavior

Xu P., Qian Y., An H., Guo H., Zhang Z., Jiang M., Huang H., Yan J.

Journal of Materials Processing Technology 339 2025年03月

ISSN  09240136

　概要を見る

Zr-4 alloy, extensively employed as cladding in nuclear reactor fuel rods, stands as the foremost line of defense for reactor safety. Given its susceptibility to defects such as micro-pores during casting and its long-term exposure to extreme conditions during practical service processes, enhancing the surface and subsurface properties of Zr-4 alloy is essential. Herein, a nanosecond pulsed laser is used to irradiate the Zr-4 alloy in a nitrogen environment to investigate the evolution of its surface and subsurface properties under the combined effects of laser heat treatment and laser gas nitriding. The experimental results reveal a remarkable augmentation in surface hardness and scratch resistance of the Zr-4 alloy after laser irradiation. Notably, the hardness of the laser-irradiated surface obtained with a laser power of 23.0 W and a scanning speed of 150 mm/s reaches 19.10 GPa, which is more than 7 times higher than that of the untreated surface (2.37 GPa). These improvements are attributed to the synergistic effects of the introduction of hard ZrN phase, the reduction of subsurface porosity, and grain refinement. This study demonstrates a promising approach for significantly improving the mechanical properties of Zr-4 alloy, holding considerable practical significance for its applications in the nuclear energy industry and other relevant fields.

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Coupled SPH-FEM Simulation Model to Analyze the Mechanism of Single Particle Impact in Abrasive Waterjet Machining

Abdelhameed Y., Maher I., Yan J., El-Hofy H., Hassan M.A.

Tribology in Industry 47 （ 1 ） 77 - 91 2025年03月

ISSN  03548996

　概要を見る

Studying single particle impact is crucial to understanding the erosion mechanism in abrasive waterjet machining (AWJM). In this paper, the finite element method (FEM) and smoothed particle hydrodynamics (SPH) were combined to investigate the mechanism of single particle impact under the waterjet influence. The particle (garnet) and workpiece (Al 7075-T6) were represented by FEM, while the waterjet was discretized using SPH. Linear elasticity and the Johnson-Cook (JC) model were selected to model the abrasive and workpiece materials, respectively. The simulation was conducted in ABAQUS where the effects of particle shape, position, and impact angle on material removal were investigated. The results of the developed model revealed that the erosion mechanism and mechanics significantly differed when considering the waterjet effect. This was primarily attributed to the dynamic phenomena resulting from the waterjet impact, including stagnation zone and drag forces. It was found that the impact angle corresponding to maximum erosion depended on the particle shape and radial position within the jet stream. The presented model has proved its capability since it offers a novel perspective on the single particle impact mechanism by incorporating the realistic dynamic phenomena accompanying the impact in AWJM.

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Fabrication of microcone arrays on Ti6Al4V by nanosecond laser nitriding

Zhang H., Wang B., Yang Z., Zhang H., Zhang Z., Huang H., Yan J.

International Journal of Mechanical Sciences 287 2025年02月

ISSN  00207403

　概要を見る

The application of titanium alloys still faces some challenges such as relatively low hardness and insufficient wear resistance. Nanosecond pulsed laser irradiation in a nitrogen atmosphere has proven to be effective for fabricating micro/nano structures on titanium alloys, enhancing surface hardness and wear resistance. However, micro/nano structures produced by line-by-line laser scanning often exhibit directional differences and surface defects such as re-deposited particles and pores. Herein, vertically crossed laser scanning in a nitrogen atmosphere was employed to address the directional difference, enabling the simultaneous fabrication of microcone arrays and nitriding layers on Ti6Al4V surface. To eliminate the surface defects on the microcone structure, laser surface finishing via defocused scanning was performed, followed by morphological analysis, bonding force evaluation, and tribological performance testing. The results showed that the area percentage of re-deposited particles on the laser-finished microcone array surface decreased from 24 % to 5 %. The bonding force of the nitriding layer was assessed using linear loading scratch tests, and the highest value of 69 N was obtained. To investigate the wear resistance of the laser-finished microcone array surface, friction and wear tests were performed. From 25 °C to 600 °C, nearly no wear grooves were observed on the tested surfaces, demonstrating excellent high-temperature wear resistance. The wear mechanism was mainly related to the cutting action of the microcone structures on the counterpart ball. This study advances the fabrication of micro/nano structures and simultaneous nitriding on titanium alloys, demonstrating the significant potential for practical applications as surface contact materials.

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Nanoindentation behavior of the laser-repaired CoCrFeNiV high-entropy alloy

Wang C., Huang W., Yi C., Jiang M., Huang H., Yan J.

Intermetallics 177 2025年02月

ISSN  09669795

　概要を見る

High-entropy alloys (HEAs) are solid-solution alloys composed of multiple elements, exhibiting excellent mechanical properties. The unique plastic deformation mechanism induced by their specific solid solution structures has attracted considerable attention but remains incompletely understood, particularly at the micro-scale. In this study, the surface morphology, chemical composition, and microstructures of CoCrFeNiV HEA before and after laser remelting repair were investigated. Nanoindentation testing was employed to characterize the surface hardness and creep behavior of the repaired surface. The distribution of surface hardness before and after laser remelting, as well as the indentation creep behavior under different loads, were studied. The mechanism of indentation creep on the repaired surface was discussed and analyzed. The effect of microstructures of HEAs, including precipitated phases and sub-grain boundaries, on dislocation-dominated micro-scale plastic deformation was elucidated by the transmission electron microscope (TEM). This study contributes to an in-depth understanding of the creep behavior and micro-scale deformation mechanisms in HEAs.

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Special Issue: The State-of-the-Art in Japanese Manufacturing Research

Kakinuma, Y; Matsubara, A; Matsumura, T; Sugita, N; Suzuki, N; Takahashi, S; Yan, JW

JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME 147 （ 1 ）  2025年01月

ISSN  1087-1357

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Femtosecond Pulsed Laser Machining of Fused Silica for Micro-Cavities With Sharp Corners

Brinkmann, M; Qian, YF; Huang, H; Yan, JW

JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME 147 （ 1 ）  2025年01月

ISSN  1087-1357

　概要を見る

Fused silica is an important material for applications requiring high temperature resistance, low thermal expansion coefficient, and excellent optical properties. The machining of micro-cavities on fused silica surfaces is of particular interest for micro-fluidic manipulation and miniaturization of high-quality optical waveguides, etc., but it still remains technically challenging for traditional manufacturing techniques. In the present study, machining of square cornered semienclosed micro-cavities on fused silica surfaces by femtosecond laser has been investigated experimentally. The effects of laser machining conditions including laser power, laser scanning speed, laser incidence angle, and laser-off delay time on the sidewall slope and bottom surface roughness of the micro-cavities were comprehensively investigated. The results indicated that laser power played an important role in determining the sidewall slope of the micro-cavity, while the laser scanning speed had a significant influence on the bottom surface roughness and subsurface damage. Furthermore, the sidewall slope of the micro-cavity was linearly increased as the laser incidence angle increases. By using a laser incidence angle of 10 deg and a laser-off delay time of 280 ms, a micro-cavity with sidewall slopes close to right angles (90 deg) was fabricated. This study demonstrates that femtosecond laser machining is an effective method for fabricating sharp cornered micro-cavities in fused silica, and the appropriate selection of laser machining conditions based on practical application scenarios is important.

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Subsurface amorphization-induced ultrasmooth and ultrahard surface during the diamond turning of polycrystalline pure copper

Wang S., He C., Wang Z., Yan J.

Materials and Design 249 2025年01月

ISSN  02641275

　概要を見る

Previous simulations indicated that pure metals can be amorphized during diamond turning. However, no pure metal has been successfully amorphized during this procedure to date. Herein, a comprehensive study on the surface formation mechanism was performed by examining the surface finish and subsurface variation characteristics. Polycrystalline pure copper was selected as the working material. In this study, the amorphization phenomenon and lattice structure transformations (from face-centred cubic to hexagonal close-packed and monoclinic structures) of pure copper were observed. The amorphization and phase transformation inside the working material depended on the tool nose radius being large, the cutting edge being sharp, and the feed rate being low. By using a large-nose-radius (10 mm) diamond tool with a sharp cutting edge (10.3 nm) at a low feed rate (0.5 μm/rev), an ultrasmooth and ultrahard surface with a 0.61 nm roughness Sa and 5.0 GPa nanohardness was achieved. Molecular dynamics simulations revealed that the high shear strain was responsible for the amorphization and lattice structure transformation during pure copper diamond turning. The findings of this study were considered critical for generating an amorphous subsurface layer in a pure metal and for achieving a ultrasmooth and ultrahard surface using single-point diamond turning.

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Nanosecond Laser Nanopatterning of Highly Ordered Nanodot Arrays on Silicon Surface: Breaking the Monopoly of Femtosecond Lasers

Qian Y., An X., An H., Huang H., Geng Y., Zhang Z., Huang W., Yan J.

Laser and Photonics Reviews 19 （ 11 ）  2025年

ISSN  18638880

　概要を見る

Laser nanopatterning is an effective strategy to manipulate the surface properties of materials. One of the glaring restrictions is that the fabrication of long-range ordered nanostructures typically relies on ultrafast lasers, especially femtosecond lasers, while the insurmountable thermal effects associated with the longer pulse durations of nanosecond lasers are deeply considered to be the nemesis of this scenario. Herein, for the first time, a nanosecond laser-based nanopatterning technique for fabricating highly ordered nanodot arrays on the monocrystalline silicon surface through a remarkably straightforward process is proposed. The mechanism involves Marangoni flow-assisted low-threshold oxidation of monocrystalline silicon induced by nanosecond laser, along with a domino-like growth process of nanodots driven by optical near-field enhancement. Finite-difference-time-domain (FDTD) simulations provide insight into the underlying origin of nanosecond laser-induced nanodot arrays. The prepared large-area nanodot arrays demonstrate a range of functionalities, including the manipulation of light reflection and diffraction, structural color, and surface-enhanced Raman scattering (SERS). The present study challenges the established view that the pronounced thermal effects associated with the long pulse durations of nanosecond lasers are incompatible with high-precision nanopatterning, which opens new avenues for research into laser-matter interactions.

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Statistical modeling and optimization of ultrasonic vibration assisted end grinding of alumina ceramics

Mansour M.M., Maher I., Nassef M.G.A., El-Hofy H., Yan J., Khairaldien W.M.

International Journal on Interactive Design and Manufacturing 2025年

ISSN  19552513

　概要を見る

Alumina is an advanced ceramic material that has numerous applications in dentistry and medicine. Ultrasonic-assisted end grinding proved to be one of the most successful and efficient ceramic processing techniques. However, the current state of the art in UAEG of alumina is mostly limited to finishing operations with low material removal rates. In this paper, UAEG is investigated to find the optimum grinding conditions of roughing operations of alumina ceramics. Response Surface Methodology was employed to study all combined effects of the spindle speed, feed rate, depth of cut, and vibration amplitude on the MRR, grinding forces and surface roughness. The surface morphology of the ground surface and the magnitude of the resultant grinding forces were recorded and analyzed for each test. The results showed that the vibration amplitude has the most influential effect on surface roughness with a contribution of 32.08%, while the grinding force is most affected by depth of cut (32.02%). The spindle speed of 9500 rpm, feed rate of 900 mm/min, depth of cut of 47 µm, and vibration amplitude of 2.6 µm are found to be the optimum machining parameters that maximize MRR and minimizing the grinding force and surface roughness.

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Surface finishing by shape-adaptive processes

Yan J., Mullany B., Beaucamp A., Meyer D., Sugita N.

CIRP Annals 2025年

ISSN  00078506

　概要を見る

Complex surfaces are increasingly used in optics, biomedical devices, and aerospace industries. Additive manufacturing and five-axis milling can produce complex shapes, but additional finishing processes are needed to meet the surface quality demands. This keynote paper reviews shape-adaptive finishing processes that enable uniform surface quality improvement without altering the shape. Key factors affecting shape adaptability, processing efficiency, and material applicability are analyzed and optimal process selection strategies for finishing complex surfaces are discussed. Future possibilities and research topics in this area, including process modeling/simulation, digital twin, surface/subsurface metrology, functionality evaluation, and applications of advanced robotics and artificial intelligence, are outlined.

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Influence of crystallinity on micro-nano structure response of Zr-based alloys treated by nanosecond laser

Qian Y., Hong J., Jiang M., Zhang Z., Huang H., Yan J.

Optics and Lasers in Engineering 183 2024年12月

ISSN  01438166

　概要を見る

Understanding the processes and mechanisms of laser-matter interaction is fundamental to the treatment of materials by using laser-based methods, but it is quite challenging because the response of matter to laser irradiation is influenced by many factors, especially the intrinsic properties of the matter. In this study, the influence of crystallinity on micro-nano structure response of Zr-based alloys (Zr41.2Ti13.8Cu12.5Ni10Be22.5) treated by nanosecond laser is investigated. The microscopic topographies and geometrical dimensions of the laser-induced micro-nano structures formed on the surface of Zr-based alloys with different crystallinity have been explored and compared. The experimental results indicate that the microstructural transformation between micro-concave and micro-convex is observed for both amorphous and crystallized Zr-based alloys, i.e., independent of the arrangement of the internal atomic structure. The geometrical dimensions of the laser-induced micro-nano structures and the critical peak laser power intensity required for the microstructural transformation are different, which can be attributed to the difference in thermal conductivity. Inspired by laser-induced micro-convex, a point-by-point laser patterning technique has been proposed for highly efficient and flexible preparation of micro-nano patterns. Importantly, this patterning technique exhibits ultra-high processing efficiency with a material accumulation rate of more than 1012 μm3/s. This work paves an avenue for understanding the laser-matter interaction and is expected to facilitate the advanced functional applications of Zr-based alloys in many fields.

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Surface morphology formation and subsurface microstructure evolution of zirconia in ultrasonic vibration-assisted burnishing

Huang W., Tsuchida T., Yan J.

Journal of Materials Processing Technology 333 2024年12月

ISSN  09240136

　概要を見る

Yttria-stabilized zirconia (YSZ) is an outstanding ceramic material with applications in dentistry, biomedical, and mechanical device, where a smooth and durable surface is required. This study employed ultrasonic vibration-assisted burnishing (UVB) to enhance the surface hardness of YSZ while simultaneously reducing its roughness. The surface topography formation, subsurface microstructure evolution, and surface hardness change of YSZ were investigated. It was found that a smooth surface with an average roughness (Ra) of 0.12 μm was achieved using UVB, representing 67.6 % reduction in surface roughness from the original sintered surface, which is attributed to the burnishing-to-cutting phenomenon during the processing. The UVB-induced compression and material densification prevented the formation of the monoclinic phase during the processing of YSZ. Grain refinement and crystal lattice distortion occurring in the subsurface layer led to an increase in surface hardness, reaching up to 19.7 % higher than that of the original sintered surface. Moreover, the UVB-processed surface demonstrated a high resistance to mechanical impacts, effectively inhibiting the tetragonal-to-monoclinic phase transformation in indentation testing. These findings demonstrate that UVB is an effective approach for enhancing the surface and subsurface properties of the material.

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