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Papers - Yan, Jiwang

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Grain visualization of FeCoCrMnNi and AlCoCrFeNi<inf>2.1</inf> high-entropy alloys by nanosecond pulse laser irradiation

Wang C., Huang H., Zhang H., Zhang L., Yan J.

Vacuum (Vacuum) 216 2023.10

ISSN 0042207X

Characterizing grains is the most common method in materials science research, but the existing techniques for grain characterization are generally expensive and time-consuming. In this study, nanosecond pulse laser irradiation with low laser fluence is attempted to visualize the grains of two typical high-entropy alloys (HEAs) with different crystal structures and elemental compositions. The effects of laser parameters and gas atmospheres on the laser visualization of grains are comparatively investigated. Under specific laser irradiation conditions, the grains of these two HEAs could be well visualized by producing different surface nanostructures. By experiments and analysis, the underlying mechanisms of laser visualization of grains under different conditions are elucidated, and the role of O element on the promotion of the visualization of grain boundaries is confirmed. This study provides a simple and efficient method to visualize the grains of HEAs, and on the other hand, enhances the understanding of nanosecond laser-HEA interaction.

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Achieving superhydrophobicity of the FeCoCrMnNi surface via synergistic laser texturing and low temperature annealing

Wang C., Huang H., Cui M., Zhang Z., Zhang L., Yan J.

Journal of Laser Applications (Journal of Laser Applications) 35 ( 3 ) 2023.08

ISSN 1042346X

Superhydrophobic surfaces are highly desirable due to their remarkable water-repellent behavior. Laser texturing with subsequent low surface energy modification is a versatile strategy for creating such surfaces. In this study, via synergistic laser texturing and low temperature annealing, superhydrophobicity was first attempted to be achieved on the FeCoCrMnNi surface. By optimizing the laser parameters, the arrays with large depth-to-width ratios were constructed. Subsequently, by annealing at a low temperature, the transition process from superhydrophilicity to superhydrophobicity was successfully achieved on the FeCoCrMnNi surface. The effects of the hatching interval on the wettability were investigated, and the mechanism of wettability transition for FeCoCrMnNi was discussed. According to the experimental results and analysis, the textured surfaces exhibited excellent superhydrophobicity at different hatching intervals and a maximum contact angle of 165° was obtained. Furthermore, the created superhydrophobic surfaces possessed good liquid capture and self-cleaning capabilities and enabled magnification for optical imaging. The wettability transition after low temperature annealing was attributed to the absorption of airborne organic compounds. This study provides an efficient, clean, and versatile strategy to achieve superhydrophobicity of the FeCoCrMnNi surface by laser processing.

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Laser repairing of FeCoCrNiV high-entropy alloy and its mechanical and cutting characteristics

Wang C., Huang H., Zhang H., Zhang L., Yan J.

Journal of Materials Processing Technology (Journal of Materials Processing Technology) 317 2023.08

ISSN 09240136

High-entropy alloys (HEAs) are promising structural and functional materials owing to their superior mechanical and chemical properties. High surface quality and good machinability are essential for micro-machining high-end precision equipment. Here, laser repairing (LR) was firstly employed to eliminate surface defects and improve the machinability of FeCoCrNiV. After LR, the microstructures and mechanical properties of FeCoCrNiV were investigated. The results show that the surface morphology and chemical composition uniformity of FeCoCrNiV were significantly improved after LR, in which the high melting-point V-rich precipitates concentrated on the original surface were homogeneously distributed throughout the substrate. The surface hardness decreased from 10.5 to 4.5 GPa due to the growth of grains, and the hardness distribution became more homogeneous after LR, providing the opportunity to improve its machinability. In ultrasonic vibration diamond turning tests, the machined surface quality, tool wear, and cutting chips indicated that the laser-repaired material exhibited superior machinability. A sinusoidal free-form surface with high surface quality was then constructed by ultrasonic vibration-assisted diamond turning on the laser-repaired surface. This study provides a method to repair surface defects of HEAs and improve their machinability, which is beneficial to their practical applications.

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Mechanisms of tool-workpiece interaction in ultraprecision diamond turning of single-crystal SiC for curved microstructures

Huang W., Yan J.

International Journal of Machine Tools and Manufacture (International Journal of Machine Tools and Manufacture) 191 2023.07

ISSN 08906955

Single-crystal silicon carbide (SiC) is one of the most attractive materials for electronics and optics but extremely difficult to cut owing to its hard and brittle properties. While in previous studies, the focus has been placed on machining flat surfaces, in this study, the mechanisms of tool-workpiece interaction in cutting curved microstructures on 4H–SiC (0001) were explored through the ultraprecision diamond turning of micro-dimples. The surface/subsurface of both machined workpieces and used diamond tools were characterized, and the machining characteristics, such as chip formation and cutting forces, were also investigated. It was found that microcracks occurred easily in the feed-in/cut-in area of the dimples, which is caused by a large friction-induced tensile stress due to a large thrust force. The dimples located on the secondary cleavage directions <10−10> (S-dimples) were easy to produce crack-free surfaces, while the dimples located on the primary cleavage directions <−12−10> (P-dimples) were very prone to cause cracks on surfaces, even though the chips were formed in a ductile mode. The dimples located on the in-between direction (I-dimples) were moderately prone to surface cracking. It was also found that although the S-dimple has a crack-free surface, it has the thickest subsurface damage (SSD) layer containing a disordered layer, dislocations, and stacking faults; the SSD layer of the P- and I-dimples do not contain stacking faults; and the SSD layer of the I-dimple is the thinnest. Flank wear with nanoscale grooves on the diamond tool was significant without edge chipping and diamond graphitization detected. By optimizing the cutting conditions, a crack-free micro-dimple array was fabricated with nanometric surface roughness. The findings from this study provide guidance for the manufacture of curved SiC parts with high surface integrity, such as molds for replicating microlens arrays and other freeform surfaces on glass.

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A theoretical and deep learning hybrid model for predicting the surface roughness of diamond-turned polycrystalline materials

He Chunlei, Yan Jiwang, Wang Shuqi, Zhang Shuo, Chen Guang, Ren Chengzu

International Journal of Extreme Manufacturing (International Journal of Extreme Manufacturing) 5 ( 3 ) 2023.06

ISSN 2631-8644

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Antireflective structured surface of chalcogenide glass fabricated using glass to glass molding

Zhu Z., Zhou T., He Y., Yu Q., Wang X., Yan T., Yan J., Ruan H.

Ceramics International (Ceramics International) 49 ( 17 ) 28216 - 28223 2023.06

ISSN 02728842

Chalcogenide (ChG) glasses with micro-nano structure arrays are increasingly demanded in infrared optical systems owing to their excellent antireflective properties, and can be mass-produced by precision glass molding (PGM). Nickel-phosphorus (Ni–P) plated molds are commonly used in the PGM process, but the Ni atoms tend to react with the ChG glass at high temperatures. In this study, we propose a novel two-step PGM process. A Ni–P mold is used to transfer antireflective micro-nano structure array to silicate glass. Then the silicate glass, which has a higher glass transition temperature (Tg) than the ChG glass, is used as the mold to replicate the antireflective structured surface to the ChG glass. The results show that the ChG glass micro-nano structure array has high forming accuracy and favorable infrared optical transmission characteristics. The silicate glass is proved to be an appropriate mold material for the ChG glass molding process. This work provides a novel type of the PGM techniques for ChG glass materials.

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Microgrooving of ferrous metals by using cBN tools with laser-modified edges

D. Kitagawa, T. Meshram J. Yan

Journal of the Japan Society for Abrasive Technology 67 ( 6 ) 341 - 346 2023.06

Research paper (scientific journal), Joint Work, Corresponding author, Accepted

A novel calibration method for angular misalignment in independently controlled fast tool servo-based diamond turning

Tanikawa S., Sato Y., Yan J.

Precision Engineering (Precision Engineering) 83 216 - 227 2023.06

ISSN 01416359

With significant technological progress in optics fields, such as VR and 3D sensing technologies, the demand for optical components with complex shapes (e.g., freeform surfaces) has expanded significantly in recent years. Ultra-precision diamond turning is one of the common manufacturing methods used for freeform optics. There are two tool-motion mechanisms for freeform diamond turning: slow tool servo (STS), which moves the entire tool rest, and fast tool servo (FTS), which only drives the diamond tool. In particular, high-frequency and long-stroke FTS units driven by a separate control system from the machine tool controller have recently been developed as a new trend in FTS-based diamond turning. However, this type of independent FTS control system causes a time delay between the machine tool instruction and the FTS tool motion. Even a millisecond-scale time delay can cause a considerable angular misalignment owing to the high rotation rate of the spindle, resulting in a micron-scale form error on the workpiece surface. In this paper, a novel method for precisely measuring the time delay from the machined workpiece surface and compensating for the misalignment based on the measured time delay was proposed. To measure the time delay, spherical dimples were machined on the workpiece surface by using STS and FTS. Subsequently, the angular misalignment and time delay were obtained by comparing the measured surface profiles at specific positions of the spherical dimples. Thus, the time delay can be measured with microsecond-scale accuracy. Based on the measured time delay, the shifted tool position along the spindle axis by the time delay was compensated to the ideal tool position by considering the cutting velocity. Consequently, the angular misalignment was completely eliminated, and submicron-level form accuracy was achieved. This calibration method of angular misalignment for an independent FTS unit is expected to significantly improve the accuracy of ultra-precision machining of freeform optics.

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Tailoring the surface characteristic of metallic glass for wettability control

Qian Y., Liu H., Zhang L., Jiang M., Huang H., Yan J.

Journal of Materials Research and Technology (Journal of Materials Research and Technology) 24 7040 - 7046 2023.05

ISSN 22387854

Bulk metallic glasses (BMGs) have attracted broad research interest in industrial and commercial fields due to their outstanding mechanical and physical properties. Achieving controlled manipulation of their surface wettability is expected to further improve their applicability. In this study, the functional MG surfaces with various wetting behaviors (including superhydrophilicity, superhydrophobicity, gradient wettability, coexistence of superhydrophilicity and superhydrophobicity) were fabricated by controlling the surface microstructure and chemical composition, which were achieved by laser processing and low-temperature heat treatment. The laser-patterned MG surface with hierarchical micro/nanostructures showed hydrophilicity, and it turned to hydrophobicity after heat treatment, which could be attributed to the adsorption of organic matter from the ambient air. The fabricated gradient wetting surface achieved directional transport of droplets, and the constructed extreme wetting contrast surface exhibited good ability in controlling the spreading of droplets.

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The scratch characteristics of laser nitrided Zr-based metallic glass surface

Hong J., Wu H., Huang H., Zhang L., Zhang Z., Jiang M., Yan J.

Intermetallics (Intermetallics) 155 2023.04

ISSN 09669795

Improving the surface hardness and tribological characteristics of metallic glasses (MGs) is meaningful for their applications as surface contact materials. In this study, nanosecond laser nitriding was performed on Zr-based MG to improve its surface properties. Three types of laser nitrided surfaces with different hardness were prepared, and their tribological characteristics were systematically investigated by means of the scratch test. The experimental results indicated that compared with the as-cast MG, the hardness of these three laser nitrided surfaces was increased by 47.94%, 114.56%, and 171.99%, and their coefficients of friction were reduced by 29.12%, 65.05%, and 71.84%, respectively. Furthermore, the residual scratches and surrounding chips exhibited various features under different conditions, and the scratch damage mechanisms were analyzed accordingly.

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Study on the non-free plastic shear removal of material and cutting-induced deformation of micron-submicron grooves

He Y., Zhou T., Kumar A.S., Wang X., Yan J.

Journal of Materials Processing Technology (Journal of Materials Processing Technology) 317 2023.04

ISSN 09240136

The shear interference and chip removal interference between different tool edges during non-free cutting are the main reasons for the deformation of micron-submicron grooves. To our best knowledge, the understanding of the non-free cutting of micron-submicron grooves is still not well established. This paper provides new insight into the material removal mechanism and cutting-induced deformation of micron-submicron grooves in non-free cutting. A novel variable shear angle removal model, revealing the difference of material shear at different positions of the tool edge, is established by infinitesimally segmenting the tool edge after analyzing the shear interference and chip removal interference mechanisms. An equation of the local shear angle enables the mathematical derivation of the topography of the shear surface and chip cross-section in the non-free cutting of micron-submicron grooves. The distribution of shear stress in the shear zone is calculated by establishing the relationship between the shear angle and shear stress based on the unequal division shear zone (UDSZ) theory and Johnson-Cook theory. Furthermore, a mechanics model of micron-submicron groove cutting, revealing the deformation mechanism of the micron-submicron grooves, is established using the differential cutting force method. Finite element simulations and high-speed cutting experiments are conducted to analyze the cutting microstate between the tool and the material and the dynamic deformation of the micron-submicron grooves during non-free cutting. The stress trend of the elastic nodes on the tool edge verifies the mechanics model, and the chip morphology verifies the formation of the shear surface and chips. The degree of non-free cutting is higher at the tool edge infinitesimal segments (TEISs) closer to the tool tip, resulting in a smaller shear angle, which makes the extrusion stress suffered by the groove increases nearly twice from top to bottom. The material flow due to dynamic deformation causes the relative cutting line of the rear-side tool edge to shift forward. The deformation of the micron-submicron grooves is related to the stiffness of the structure.

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Generation of nanopore structures in yttria-stabilized zirconia by femtosecond pulsed laser irradiation

Yamamuro Yuka, Shimoyama Tomotaka, Yan Jiwang

Journal of Materials Research and Technology (Journal of Materials Research and Technology) 23 1155 - 1176 2023.03

ISSN 2238-7854

Femtosecond pulsed laser irradiation of yttria-stabilized zirconia (YSZ) was performed to investigate the feasibility and fundamental characteristics of nanopore structure fabrication. Numerous nanopores were successfully generated on the YSZ surface with only a single laser pulse shot by controlling laser power near the ablation threshold. The nanopore generation mechanism involves light focusing by the convex shape of a crystal grain and ablation inside the grain. By increasing laser power, the number of nanopores increased. Cross-sectional observation revealed that the depth of nanopores was about 500 nm, and nanopores were generated inside the YSZ grains of the top layer while keeping the grains' shapes unchanged. It was found that higher scanning speed and a small number of scans enabled nanopores fabrication without changing the original surface shape, avoiding the removal of the surface layer. Laser-irradiated surfaces of YSZ were characterized by Raman spectroscopy, and it was found that there was no significant phase change in the specimen after nanopore generation compared with the original YSZ surface, confirming that there was no thermal damage to the bulk material. The surface with nanopores showed an enhancement in surface hydrophilicity. These findings demonstrated the possibility of selectively generating nanopores in the top surface of YSZ for use in functional surfaces without serious thermal damage to the workpiece. It is expected that the nanopore generation will lead to new applications of YSZ.

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Significant improvement in surface hardness of Zr-based metallic glass by nanosecond pulsed laser irradiation in graphite powder water suspension

Zhang H., Qian Y., Zhang L., Jiang M., Huang H., Yan J.

Surface and Coatings Technology (Surface and Coatings Technology) 454 2023.02

ISSN 02578972

Metallic glasses (MGs) have shown promising application prospects as structural materials due to their unique mechanical properties. While, for broadening their application as functional materials, significant improvement in surface hardness of MGs is required. Accordingly, in this study, laser carbonization of MGs was attempted by irradiating the Zr-based MG surface immersed in graphite powder water suspension using a nanosecond pulsed laser. Nanoindentation response and surface morphologies of the initial and irradiated surfaces were characterized in detail. The results indicated that the hardness of the laser-irradiated surfaces was increased by 130 %–200 % (from 6.407 GPa to 19.193 GPa), and as well, the serrated flows in load-depth curves and the surface shear bands around the residual indent disappeared, suggesting the change in micro-scale plastic deformation behaviors of the laser-irradiated surfaces. Furthermore, the chemical composition of the initial and irradiated surfaces was analyzed by X-ray diffraction (XRD) and energy dispersive spectrometer (EDS), which showed that the irradiated surfaces were carbonized in the graphite powder water suspension. Accordingly, the increase in surface hardness was due to the formation of the hard crystalline phases.

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Repairing surface defects of Zr-based metallic glass ribbons by nanosecond pulsed laser irradiation

Wang J., Zhang H., Zhang Z., Hong J., Qian Y., Huang H., Yan J.

Manufacturing Letters (Manufacturing Letters) 35 48 - 52 2023.01

ISSN 22138463

The metallic glass ribbons (MGRs) industrially produced by the single roller melt-spun method have many surface defects such as pits and scratches. In this study, it was attempted to repair the surface defects of Zr-based MGRs via nanosecond pulsed laser irradiation. The experimental results showed that the roughness of laser-repaired surfaces was significantly reduced compared to the melt-spun surface, and the surface topographies and morphologies were sensitive to the laser parameters. With optimal laser parameters, the smooth and defect-free surface could be achieved. This work offers a convenient and high-efficiency approach for repairing the surface defects of MGRs.

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Life-cycle assessment of the laser sintered-silicon anode for lithium ion battery production

Hendrickx B., Yan J., Duflou J.

Procedia CIRP (Procedia CIRP) 116 594 - 599 2023

ISSN 22128271

As the global market for lithium-ion batteries continues to grow, sourcing alternative materials for battery cell production gains interest and has an ever increasing potential to reduce environmental impact during the production phase. Around 97% of the produced Li-ion batteries contain a graphite-based anode, coated on a copper foil. In this Life Cycle Assessment the potential reduction of environmental impact over various categories during the production of batteries when using an anode production method by laser sintering Si-waste powder in an innovative process is investigated. The study provides an indication of environmental feasibility of the suggested production process, comparing the technical innovative process to currently available anode production processes. The impact comparison is made on the level of anode production (cradle to gate) with the potential to zoom out to the full battery production process in future work. Current results indicate that the overall impact of production increases 27% when using the suggested anode production process, with the results being sensitive to the amount of energy required for sintering and the allocation of impact towards the Si-waste. The impact of this switch of anode production method for the full Li-ion battery production will depend on the affected charge capacity and lifetime duration of an assembled battery module.

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Nanosecond Laser “Pulling” Patterning of Micro–Nano Structures on Zr-Based Metallic Glass

Cui M., Huang H., Zhang L., Yan J.

Small (Small) 19 ( 14 ) 2023

ISSN 16136810

Flexible and controllable fabrication of micro–nano structures on metallic glasses (MGs) endow them with more functional applications, but it is still challenging due to the unique mechanical, physical, and chemical properties of MGs. In this study, inspired by a new physical phenomenon observed in the nanosecond laser–MG interaction (i.e., the surface structure is transformed from the normally observed microgroove into the micro–nano bulge at a critical peak laser power intensity), a nanosecond laser “pulling” method is proposed to pattern the MG surface. The formation mechanism and evolution of the micro–nano bulge are investigated in detail, and accordingly, various micro–nano structures including the unidirectional stripe, pillar, cross-hatch patterns, “JLU”, circle, triangle, and square, are derived and created on the MG surface, which affects the surface optical diffraction. Overall, this study provides a highly flexible and controllable method to fabricate micro–nano structures on MGs.

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Fabrication and functional characteristics of micro/nano structures on the RB-SiC surface through nanosecond pulsed laser irradiation

An H., Qian Y., Zhang L., Zhang Z., Huang H., Yan J.

Ceramics International (Ceramics International) 49 ( 22 ) 36276 - 36288 2023

ISSN 02728842

Reaction-bonded silicon carbide (RB-SiC) is gaining increasing attention due to its exceptional mechanical properties contributed by the dispersion of hard silicon carbide (SiC) and silicon (Si), which has been extensively applied in aerospace and automobile industries. Fabrication of micro/nano structures on the RB-SiC surface can endow it some specific functional properties, but conventional manufacturing procedures face challenges due to the intrinsic hard-brittle nature of RB-SiC. In the present study, various micro/nano structures, including dome-like particle structures, micro-cone structures and the spider web-like film, are fabricated on the RB-SiC surface by nanosecond pulsed laser irradiation under different experimental conditions. Comparative experiments are performed to explore the effects of laser power and scanning speed on the microscopic morphology and chemical composition. Consequently, the ablation mechanism is clarified. The formation of micro-cone structures covered by the spider web-like film can result in a wettability transition of the RB-SiC surface from hydrophilicity to superhydrophilicity. In addition, by introducing the spider web-like film, the reflectivity of the RB-SiC surface is increased by an impressive 83% or more in the wavelength range of 200 to 2500 nm. This study provides a method for improving the surface properties of RB-SiC substrates using a laser-based approach, which is anticipated to expand their application prospects as functional materials.

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Effects of process parameters on cutting forces, material removal rate, and specific energy in trochoidal milling

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

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science (Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science) 238 ( 7 ) 2745 - 2757 2023

ISSN 09544062

Trochoidal milling has been developed to enhance tool life during slot machining. It is characterized by reduced cutting forces, cutting temperature, and tool wear as compared to conventional milling processes. It is effective in machining difficult-to-cut materials, high-speed machining, and groove corners. However, this process has not been deeply investigated enough to discover its advantages and optimize its parameters. A full factorial design of 144 experiments has been applied in this paper to investigate extensively the effects of axial depth of cut, feed rate, and trochoidal step on material removal rate, cutting forces, and specific energy in trochoidal milling. Trochoidal step and axial depth of cut almost have the same contributions on cutting forces by 32% and 31% respectively, followed by feed rate by 25%. Feed rate, trochoidal step, and axial depth of cut influence the material removal rate by 37%, 30%, and by 19% respectively. The contributions of feed rate, trochoidal step, and axial depth of cut on relative specific energy are 57%, 24%, and 8% respectively. The increase of axial depth of cut increases the maximum resultant force till a threshold value, then it stabilizes. This behavior occurred due to the increase of the maximum engagement angle to a certain limit, then it does not increase any more. Both feed rate and trochoidal step linear affect maximum resultant force and material removal rate, while the relationships are non-linear for specific energy. It is recommended to machine slots in full depth with the highest possible trochoidal step and feed rate, considering the increase of tool wear and surface roughness. It is preferred to use a cutting tool of a large helix angle and small diameter to reduce the threshold axial depth of cut. Overall, this study is significant in characterizing, designing, and optimizing of trochoidal milling through experimental work.

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Effect of tool geometry on ultraprecision machining of soft-brittle materials: A comprehensive review

Huang W., Yan J.

International Journal of Extreme Manufacturing (International Journal of Extreme Manufacturing) 5 ( 1 ) 2022.12

ISSN 26318644

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Design and fabrication of micro and nano surface structures for enhancing metal–polymer adhesion using femtosecond laser treatment

Omiya M., Nakajima A., Yan J.

Materials and Design (Materials and Design) 224 2022.12

ISSN 02641275

This study investigated the effects of micro- and nanostructures on the adhesion strength between copper and an encapsulating mold compound (EMC). The shape of the microgrooves was designed based on fracture mechanics theory, and the effect of laser-induced periodic structure surface (LIPSS) formation on the microgroove was investigated using numerical simulations. The designed surface profiles were fabricated using femtosecond laser treatments, and the adhesion strength between copper and the EMC was evaluated. The results show that deep microgrooves improved the adhesion strength owing to the anchor effect. However, the aspect ratio between the pitch and depth of the microgroove had a limitation in enhancing the adhesion strength. The formation of LIPSSs on the mountaintop of the microgroove was very effective; however, an LIPSS on the valley of the microgroove was ineffective. Numerical analyses revealed that LIPSSs suppressed the shear deformation of the EMC and worked as resistance to interface delamination. Based on the findings obtained in this study, combining micro- and nano-scale surface structure formation with femtosecond laser treatments is an effective and eco-friendly method for improving adhesion strength.

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