論文 - 閻　紀旺

A comparative study on mechanical polishing and laser polishing of laser-nitrided Zr-based metallic glass surface

Hong J., Zhang L., Zhang Z., Huang H., Yan J.

International Journal of Advanced Manufacturing Technology （International Journal of Advanced Manufacturing Technology）  124 （ 3-4 ） 959 - 971 2022年

ISSN  02683768

　概要を見る

As a promising surface modification method, nanosecond pulsed laser nitriding has been widely employed in enhancing the surface hardness and chemical corrosion of Zr-based metallic glass (MG). However, laser nitriding generally leads to poor finished surface quality, limiting its potential applications. For flattening the laser-nitrided surface, the most common methods, i.e., mechanical polishing (MP) and a novel proposed flattening approach, laser polishing (LP), were comparatively studied. A systematical comparison between MP and LP on three types of laser-nitrided surfaces was performed to evaluate the surface roughness, surface hardness, and plastic deformation. The experimental results indicate that the surface roughness of these three laser-nitrided surfaces is reduced by 56.4%, 58.1%, and 44.6% by MP. In contrast, a remarkable improvement in the surface quality is achieved with a maximum reduction in surface roughness by 80.4%, 81.5%, and 74.2% by LP, respectively. While in terms of the surface mechanical properties, the LP surfaces exhibit slightly lower hardness than the corresponding MP surfaces, which are both enhanced in hardness compared with as-cast MG. Additionally, no matter on the MP or LP surfaces, the shear bands and serrated flows have been significantly suppressed compared with as-cast MG, demonstrating that the micro-scale plastic deformation of as-cast MG has been modified. Although the obtained results indicate that the surface roughness of the laser-nitrided surface could be improved by both MP and LP, in terms of environmental friendliness, flexibility, and controllability, the LP shows dominant advantages and enormous potential in industry and consumer products.

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Optimization of fast tool servo diamond turning for enhancing geometrical accuracy and surface quality of freeform optics

Zhang L., Sato Y., Yan J.

European Society for Precision Engineering and Nanotechnology, Conference Proceedings - 22nd International Conference and Exhibition, EUSPEN 2022 （European Society for Precision Engineering and Nanotechnology, Conference Proceedings - 22nd International Conference and Exhibition, EUSPEN 2022）     491 - 494 2022年

　概要を見る

Fast tool servo (FTS) diamond turning is a promising technique for high-precision generation of freeform optics with remarkable efficiency. However, the conventional constant scheme for control point sampling fails to consider the surface variation, which might lose some details of the surface profile and result in low form accuracy and non-uniform surface quality. Facing this issue, this manuscript proposes a novel optimization method for control points sampling, which restrains the deviations and contains as much of the surface details. In the optimization method, the sampling intervals between two adjacent control points are actively adjusted to adapt the surface variation of the desired surface. By adopting this method, the sampling induced interpolation error between the control points is restrained within the tolerance and eliminates lack/over-definition of control points in the machining area. The feasibility of the proposed optimization method is demonstrated by both theoretical prediction and fabrication experiment of sinusoid freeform surface. Compared with the conventional sampling method, both the predicted and measured form error of the proposed method are remarkably reduced about 35 % with the same amount of control points. This technique provides a new route to sampling control points in FTS diamond turning to achieve high accuracy and flexible fabrication of freeform surface machining.

New insights into the mechanisms of ultrasonic vibration cutting of brittle materials via multi-cyclic nanoindentation

Huang W., Yan J.

European Society for Precision Engineering and Nanotechnology, Conference Proceedings - 22nd International Conference and Exhibition, EUSPEN 2022 （European Society for Precision Engineering and Nanotechnology, Conference Proceedings - 22nd International Conference and Exhibition, EUSPEN 2022）     501 - 504 2022年

　概要を見る

Ultrasonic vibration cutting is a potential method for ductile machining of brittle materials. Although there are some research works trying to answer why the ultrasonic vibration promotes ductile machining of brittle materials, most of them are based on geometrical and kinematic analysis. In this study, plunge-cutting experiments under the conventional and vibration-assisted cutting conditions were conducted on single crystalline silicon and the results were compared to those of multi-cyclic nanoindentation tests. The surface morphology and subsurface microstructure of both machined grooves and residual indents were characterized. Results of plunge-cutting experiments show that with ultrasonic vibration cutting, the critical depth of cut for ductile-to-brittle transition and the amorphous phase in cutting chips are increased compared with conventional cutting. Results of multi-cyclic nanoindentation tests show that the indentation-induced amorphous layer increased as the cyclic number increased, which is consistent with the cutting results. The findings from this study may help understand the removal mechanism of brittle materials during ultrasonic vibration cutting.

Surface functionalization of Zr-based metallic glass by direct nanosecond laser texturing

Yongfeng Qian and Minqiang Jiang and Zhiyu Zhang and Hu Huang and Jiwang Yan

Vacuum （Elsevier {BV}）  194   110635 2021年12月

ISSN  0042207X

　概要を見る

The functional properties of metallic glasses (MGs) can be enhanced by introducing special micro/nano-structures on their surface. In this study, a nanosecond pulsed laser was used to texture micro-convex array structures with different pitches (P) on a Zr-based MG surface to enrich its engineering applications. The reflection characteristics and wettability of polished and textured surfaces were compared. The experimental results showed that unlike the bright spot reflected from the polished surface, the light reflected from the textured surface would induce a well-defined diffraction pattern. In addition, the wettability of the surfaces covered with micro-convex array structures was also different from that of the polished surface. That is, without post-processing, the textured array structures would promote hydrophilicity; while after exposing in the air for 100 days or fluoroalkylsilane modification, the textured array structures facilitated hydrophobicity.

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Evolution and control of deformation mechanisms in micro-grooving of Zr-based metallic glass

Qiu P., Meng B., Xu S., Rong Y., Yan J.

Journal of Manufacturing Processes （Journal of Manufacturing Processes）  68   923 - 931 2021年08月

ISSN  15266125

　概要を見る

The evolution of deformation mechanisms with increasing depth of cut (DOC) in micro-grooving of Zr-based metallic glass was deeply investigated in this study for the first time. The micro-grooving characteristics of metallic glass were initially studied by nanoscratch test, which verified that the material removal mode abruptly changes from extrusion mode to cutting mode with increase of DOC. Based on the free-volume theory, a dynamic model coupling stress, temperature and free volume concentration was used to simulate the change of deformation characteristics with DOC. The results showed that the deformation mechanism of metallic glass is closely related to free volume flow, which is significantly affected by average strain rate and free volume flow coefficient in deformation zone and can be tuned with different DOC. Considering that free volume flow is determined by its flow coefficient and concentration, we proposed to control the deformation characteristics of metallic glass in micro-grooving by heat treatment and verified its effectiveness experimentally.

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On the transformation between micro-concave and micro-convex in nanosecond laser ablation of a Zr-based metallic glass

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

Journal of Manufacturing Processes （Journal of Manufacturing Processes）  68   1114 - 1122 2021年08月

ISSN  15266125

　概要を見る

Understanding the physical mechanism of laser-material interaction is significant and meaningful in both pure science and engineering applications. Laser ablation induced micro-concave is a commonly-observed phenomenon, but the formation of micro-convex by laser ablation is rarely reported. In this study, the transformation in surface microstructure from micro-concave to micro-convex, then to micro-concave again was reported for the first time in laser ablation of a typical Zr-based metallic glass (MG). The experimental results indicated that such transformations strongly depended on the peak laser power intensity and number of laser pulses. The coupling effects of the recoil pressure and Marangoni flow were proposed to explain the observed transformation. By locally overlapping adjacent micro-convexes, various surface patterns could be fabricated on the MG surface, which could tune its surface wettability. This study would not only enhance the understanding of laser-MG interaction but also provide new methods for patterning MG surface.

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Evolution of high-pressure metastable phase Si-XIII during silicon nanoindentation: A molecular dynamics study

Zhang L., Yan J.

Computational Materials Science （Computational Materials Science）  191 2021年04月

ISSN  09270256

　概要を見る

© 2021 Elsevier B.V. Berkovich indenters are widely employed in nanoindentation experiments of single-crystal silicon, in molecular dynamic simulations of silicon nanoindentation, however, spherical indenters are generally employed. To close this gap, in this paper, a series of molecular dynamic simulations are conducted on (0 0 1), (1 0 1), and (1 1 1) silicon surfaces to explore the evolution of high-pressure phases. Several possible silicon phases are tracked by coordination number (CN), radial distribution function (RDF), and angular distribution function (ADF). Results show that the metastable phases and the high-pressure phases present different symmetrical patterns along different crystallographic orientations. A large amount of high-pressure phase Si-XIII, which is seldomly observed in nanoindentation using a spherical indenter, is first discovered under the Berkovich indenter, and the evolution mechanism is characterized by tracking the position transition of labeled silicon atoms. As a transition phase for high-pressure phase Si-II and Si-XIII, bct5 phase is found in the {1 1 1} [1 1 0] slip systems, which is related with slipping flatten lattice structures. Different from the phase transformation criterion for Si-II, the transformation from Si-I to Si-XIII companies with the local elastic deformation of (0 0 1) surface. The atoms in the three neighboring unit cells are compressed into a uniform long-distance ordered crystal structure. Upon indenter extraction and rapid stress releasing, the elastic deformation of the crystal surface resumes incompletely. A part of Si-XIII recovers to pristine Si-I and the rest changes into amorphous phase. The distribution of local hydrostatic pressure and von Mises stress in the phase transformation regions indicates that the concentrated hydrostatic pressure and specific stress induce this high-pressure silicon phase. This research clarifies the evolutionary process of Si-XIII phase generation and enriches fundamental understanding on the mechanisms of silicon phase transformations in nanoindentation.

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Annealed high-phosphorus electroless Ni–P coatings for producing molds for precision glass molding

Yu Q., Zhou T., He Y., Liu P., Wang X., Jiang Y., Yan J.

Materials Chemistry and Physics （Materials Chemistry and Physics）  262 2021年04月

ISSN  02540584

　概要を見る

© 2021 Elsevier B.V. An annealed high-phosphorus electroless Ni–P coating was developed as the mold material for precision glass molding. The coating with a phosphorus content of 11.6 wt% was prepared on heat-resistant stainless steel via an intermittent ultrasonic-assisted electroless plating method. The effects of annealing temperature and heating rate on phase transformation, grain size variation, and mechanical properties were investigated. An annealing temperature of 600 °C with a heating rate of 5 °C/min was determined to be the optimal choice for heat treatment. Microgrooves were machined on the coating surface. After heat treatment, the increased hardness and modulus helped the microgrooves on the coating resist thermal deformation during the PGM process. The PV value decreased from 0.58 to 0.32 μm, and the surface roughness decreased from Sa 104.5 to Sa 62.6 nm. The mold produced by heat-treated coating was beneficial for improving the forming accuracy of precision glass molding.

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Deterministic error compensation for slow tool servo-driven diamond turning of freeform surface with nanometric form accuracy

Nagayama K., Yan J.

Journal of Manufacturing Processes （Journal of Manufacturing Processes）  64   45 - 57 2021年04月

ISSN  15266125

　概要を見る

© 2021 The Society of Manufacturing Engineers Slow tool servo (STS) turning takes an important role in fabrication of freeform optical elements. However, in conventional STS turning, it is technologically difficult to obtain nanometer-level form accuracy due to multiple error factors such as tool trajectory errors, tool alignment errors and dynamic follow-up errors of machine tools used. In this study, a deterministic process flow was proposed where all the main error factors were comprehensively analyzed, simulated and then compensated before machining based on the feedforward method, and the workpiece form error after compensation was predicted accurately. The proposed process flow enabled achieving nanometer-level form accuracy by a single cut without the necessity of repetitive trial-and-error. To demonstrate the effectiveness of the proposed method, cutting tests of a two-dimensional sine wave grid were attempted on single-crystal silicon and the proposed error compensation was applied. As a result, the form error was reduced to 8 nm P–V (peak to valley) with a surface roughness of 1 nm Sa by a single cut.

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Diffraction manipulation of visible light with submicron structures for structural coloration fabrication

He Y., Zhou T., Dong X., Zhu Z., Yu Q., Liu P., Zhao W., Wang X., Hu Y., Yan J.

Optics Express （Optics Express）  29 （ 6 ） 9294 - 9311 2021年03月

　概要を見る

© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement The structural coloration of glass induced by submicron structures is eco-friendly, ink-free, and has profound scientific significance. However, it is difficult to manufacture the submicron structures for glass optics due to the high hardness of glass and the miniature size of the microstructures. In this paper, the diffraction manipulation mechanism of groove shape to structural coloration and optimization theory are studied by establishing the theoretical and simulation mode. Moreover, a newly-developed axial-feed fly-cutting (AFC) technology and the PGM technology are introduced to precisely create the designed submicron V-shape grooves and structural color pattern on a Ni-P mold and then replicating them on a glass surface. Between these two kinds of typical submicron grooves that can be machined by mechanical cutting technology, it is found that the diffraction intensity and efficiency of V-shape grooves are higher than these of jagged-shape grooves, which indicates that V-shape grooves is more suitable to be used for structural coloration with high brightness. The structural color resolution is dramatically increased with the reduction of groove spacing and can be flexibly regulated by AFC, which significantly contributes to the structural coloration manufacturing. Structural pixel segments composed of submicron grooves are arranged row-by-row to form color patterns, and the letters of different colors are fabricated on the mold and transferred to the glass surface. Methods of optical diffraction manipulation, flexible manufacturing of submicron structures, and structural color image construction proposed in this paper for the production of a structural color pattern are beneficial to a wide range of fields.

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Chip-free surface patterning of toxic brittle polycrystalline materials through micro/nanoscale burnishing

Huang W., Yan J.

International Journal of Machine Tools and Manufacture （International Journal of Machine Tools and Manufacture）  162 2021年03月

ISSN  08906955

　概要を見る

© 2021 Elsevier Ltd Brittle crystalline materials have important applications in optics and optoelectronics. However, their powders are highly toxic; thus, the chips generated in material removal processes such as cutting, grinding, and polishing are harmful to human health and the environment. In this study, micro/nanoscale burnishing tests were conducted on polycrystalline zinc selenide (p-ZnSe) to explore the feasibility of high-precision surface patterning of a toxic material by local plastic deformation without chip generation. The local deformation behaviours and subsurface damage formation mechanisms were investigated under dry and oil-lubricated conditions. Two types of cracks occurred when the force exceeded a critical value: cracks along the slip planes at the groove bottom and cracks along the cleavage planes at the groove edge. Below the critical force value, however, a crack-free surface was obtained with lower surface roughness than those for diamond-turned surfaces. No phase transformation was detected after burnishing, but lattice distortion appeared in the subsurface layer. A model was developed to predict the activated slip planes by calculating the maximum Schmid factors of the slip systems, and the distribution of subsurface defects was clarified by cross-sectional direct observations. It was also found that the use of a lubricating oil could greatly reduce material pile-ups around the tool. As test pieces, microgrid patterns were fabricated by crossing and overlapping the grooves, and smooth surfaces with surface roughness of 1.85 nm Sa and 4.5 nm Sa, respectively, were achieved. The findings from this study demonstrate the feasibility of chip-free surface patterning on toxic brittle polycrystalline materials by micro/nanoscale burnishing, which is an effective alternative to cutting and grinding for the fabrication of micro structured optical elements and microfluidics.

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Fundamental investigation of diamond cutting of micro v-shaped grooves on a polycrystalline soft-brittle material

Huang W., Yan J.

Journal of Manufacturing and Materials Processing （Journal of Manufacturing and Materials Processing）  5 （ 1 ）  2021年03月

　概要を見る

Fabricating micro-structures on optical materials has received great interest in recent years. In this work, micro-grooving experiments were performed on polycrystalline zinc selenide (ZnSe) to investigate the feasibility of surface micro-structuring on polycrystalline soft-brittle material by diamond turning. A photosensitive resin was coated on the workpiece before cutting, and it was found that the coating was effective in suppressing brittle fractures at the edges of the grooves. The effect of tool feed rate in groove depth direction was examined. Results showed that the defect morphology on the groove surface was affected by the tool feed rate. The crystallographic orientation of grains around the groove was characterized by electron backscatter diffraction (EBSD), and it was found that the formation of defects was strongly dependent on the angle of groove surface with respect to the cleavage plane of grain. The stress distribution of the micro-grooving process was investigated by the finite element method. Results showed that the location of tensile stresses in the coated workpiece was farther from the edge of the groove compared with that in the uncoated workpiece, verifying the experimental result that brittle fractures were suppressed by the resin coating.

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One-step fabrication of regular hierarchical micro/nano-structures on glassy carbon by nanosecond pulsed laser irradiation

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

Journal of Manufacturing Processes （Journal of Manufacturing Processes）  62   108 - 118 2021年02月

ISSN  15266125

　概要を見る

Fabrication of hierarchical micro/nano-structures on glassy carbon (GC) surface is important for the application of GC as the mold material for glass molding, but it is still challenging due to the high brittleness and hardness of the material. In this study, by using a nanosecond pulsed laser, a hierarchical micro/nano-structure, i.e., micro-dimple with ring-like nanostructure on its inner wall, was generated on the GC surface. The effects of laser parameters, such as laser irradiation time and fluence, on the formation and evolution of the hierarchical micro/nano-structure were experimentally studied. By comparative experiments with graphite, the role of amorphous nature of GC on the formation of very regular hierarchical micro/nano-structure was confirmed. The results obtained by irradiating GC in argon and nitrogen gas further indicated that the formation of hierarchical micro/nano-structure was independent of the gas atmosphere. By controlling the relative positions of point shots, various micro-dimple arrays were successfully fabricated on the GC surface which significantly changed its wetting behavior. Finally, formation mechanism of the hierarchical micro/nano-structure was discussed according to the experimental results as well as some previous literatures. This study provides a one-step method for fabricating hierarchical micro/nano-structures on the GC surface by nanosecond pulsed laser irradiation, which would be meaningful for the functional applications of GC.

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Nanosecond pulsed laser-induced formation of nanopattern on Fe-based metallic glass surface

Y Qian, H Huang, M Jiang, J Yan

Applied Surface Science, 151976 （Applied Surface Science）  577 2021年

ISSN  01694332

　概要を見る

Fe-based metallic glasses (MGs) have attracted much attention because of their cheap raw materials, outstanding soft magnetic properties and superior catalytic activity. Meanwhile, the fabrication of micro/nano-structures on its surface could further improve its functional properties. In this study, it was attempted to fabricate micro/nano-structures on a Fe-based MG (Fe52Cr13Mo12C15B6Er2, in at. %) surface by nanosecond pulsed laser irradiation technology. The surface characteristics and microstructural evolution of Fe-based MG were investigated. The experimental results showed that under different laser fluences, the laser-irradiated areas exhibited distinguished microstructures, i.e., nanoparticles, the network nanostructures or a combination of these two microstructures. Furthermore, oxygen and erbium were enriched inside the network nanostructures. By analyzing the microstructural evolution, formation mechanisms of the nanoparticles and the network nanostructures were discussed. The nanoparticles were actually caused by laser-induced element enrichment (i.e. amorphous erbium oxide) and the mismatch of its wettability with the substrate; the formation of the network nanostructures was attributed to the diffusion and connection of nanoparticles under the combined influence of recoil pressure and surface topography.

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Machinability exploration for high-entropy alloy FeCrCoMnNi by ultrasonic vibration-assisted diamond turning

Zhang L., Hashimoto T., Yan J.

CIRP Annals （CIRP Annals）  70 （ 1 ） 37 - 40 2021年

ISSN  00078506

　概要を見る

High-entropy alloy (HEA) is an emerging alloy which consists of five or more metallic elements with equimolar concentrations and exhibits excellent mechanical properties at cryogenic temperature. However, its machinability is almost unknown. In this study, high frequency one-dimensional ultrasonic vibration-assisted diamond turning (UVDT) experiments were conducted on an FeCrCoMnNi-based HEA to investigate the micro-nanoscale material removal mechanisms. Compared with conventional diamond turning, UVDT produced thinner chips, lower cutting forces, less tool wear and better surface integrity. Due to the ultrasonic vibration-assisted burnishing effect, surface scratches were significantly eliminated. A freeform surface was test-fabricated with optical-level finish.

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Effects of relative tool sharpness on surface generation mechanism of precision turning of electroless nickel-phosphorus coating

Q Yu, T Zhou, Y He, P Liu, X Wang, J Yan

Journal of Mechanical Science and Technology, 1-9 （Journal of Mechanical Science and Technology）  35 （ 7 ） 3113 - 3121 2021年

ISSN  1738494X

　概要を見る

Relative tool sharpness (RTS) is identified as the ratio of undeformed chip thickness to tool cutting edge radius. This paper studies the effects of RTS on the surface generation mechanism of precision turning of electroless nickel-phosphorus (Ni-P) coating. An R-shaped tungsten carbide (WC) tool was adopted for the face turning experiment. The cutting edge radius was 1.84 µm measured by a laser scanning confocal microscope (LSCM). The chip formation behavior, cutting forces and surface morphology were investigated under different RTS values. Results showed that the chip changes from continuous to discontinuous as RTS decreases from 0.54 to 0.27, indicating the transition of the material removal mechanism. The periodical fluctuations with small amplitudes on the machined surface are associated with the high-frequency tool-tip vibration. The low-frequency fluctuations of the cutting forces are related to the material swelling and recovery. The optimal machined surface roughness was obtained at the RTS of 0.38.

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Machinability Investigation for Cellulose Nanofiber-Reinforced Polymer Composite by Ultraprecision Diamond Turning

Kamada Yu, Yan Jiwang

International Journal of Automation Technology （富士技術出版株式会社）  15 （ 4 ） 475 - 482 2021年

ISSN  1881-7629

　概要を見る

<p>Cellulose nanofiber (CeNF)-reinforced polymer composites have wide potential applications in the manufacturing of optical and mechanical parts owing to their light weight, high mechanical strength, and optical transparency. In this study, CeNF-reinforced homogeneous polypropylene (PP-CeNF) was machined under various conditions by ultraprecision diamond turning, and the results were compared with those of pure PP without CeNF addition. The influence of CeNFs on material removal was investigated by examining the surface topography, chip morphology, cutting forces, and cutting temperature. It was found that the surface defects in pure PP cutting were surface tearing, while the surface defects of PP-CeNF were surface tearing and micro-holes induced by the pulling-outs of CeNFs. Surface tearing increased with cutting speed; pulling-outs of CeNFs were slightly affected by cutting speed but strongly dependent on the tool feed rate. Under a small tool feed rate, the surface roughness could be reduced to ∼10 nm <i>Ra</i> for PP-CeNF. The thermal effect was insignificant in the experiments, whereas the effect of strain rate-induced material hardening was dominant for both workpiece materials at a high cutting speed. This study helps to understand the mechanisms for ultraprecision cutting of CeNF-reinforced polymer composites and provides guidelines for improving the machined surface quality.</p>

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Laser nitriding of Zr-based metallic glass: An investigation by orthogonal experiments

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

Surface and Coatings Technology, 127657 （Surface and Coatings Technology）  424 2021年

ISSN  02578972

　概要を見る

Laser nitriding is a useful method to improve the surface hardness of materials, and it has been newly introduced to harden the surface of Zr-based metallic glass (MG). However, the currently achieved improvement in surface hardness is only 15.7%. To explore the potential of laser nitriding of Zr-based MG, orthogonal experiments were designed and performed in this study. By nanosecond pulsed laser irradiation in nitrogen atmosphere, the effects of laser parameters (average laser power, scanning speed, overlap rate and number of irradiation cycle) on the surface hardness of Zr-based MG were systematically investigated. The experimental results showed the highest surface hardness reached 18.21 GPa (Meyer's hardness) by orthogonal design, which is about 2 times higher than that of the as-cast MG. Furthermore, the laser affecting layer consisting of nitride phase reached tens of microns. The obtained results demonstrated that significant improvement in surface hardness could be achieved by selecting appropriate laser irradiation parameters, which would be beneficial to the engineering applications of MGs as surface contact materials.

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Tribological characteristics of electrical discharge coated layers using quarry dust suspension

CY Yap, PJ Liew, ISB Othman, MFB Abdollah, J Yan

Surface and Coatings Technology, 127895 （Surface and Coatings Technology）  428 2021年

ISSN  02578972

　概要を見る

In this research, a coating layer was formed on the tungsten carbide cobalt (WC-Co) substrate surface by using electrical discharge coating (EDC) with waste quarry dust powder suspension. The tribological test was carried out by using a micro pin-on-disc tribometer at a constant normal load (10N) and sliding speed (5 mm/s). The surface roughness, Vickers micro-hardness, coefficient of friction (CoF), wear weight loss, wear scar depth and wear track morphology of the coating layer were investigated and compared with the original surface of the WC-Co substrate in this study. The results indicated that under coating conditions of 5 A of peak current (Ip) and 300 μs of pulse on time (Ton), the Vickers micro-hardness increased by 28%, and the surface roughness, CoF, wear weight loss, and wear scar depth of coating layer reduced by 29%, 61%, 79%, 63%, respectively compared with the original WC-Co substrate. These results demonstrated that the coating layers produced by EDC with quarry dust waste powder suspension had good wear resistance, which could be beneficial to the cutting tool, mold and die industries.

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Laser induced micro-cracking of Zr-based metallic glass using 10¹¹ W/m² nano-pulses

Huang H., Qian Y., Wang C., Yan J.

Materials Today Communications （Materials Today Communications）  25 2020年12月

　概要を見る

© 2020 Elsevier Ltd Low power nanosecond laser irradiation has potential applications in surface processing of metallic glasses (MGs). However, the response of MGs to a relatively low power intensity (1011 W/m2) has not been investigated. In this study, surface microstructures and characteristics of Zr-based MG after low power nanosecond laser irradiation were studied. Micro-cracks with depth in nanoscale and width in microscale were observed on the irradiated MG surface. The effects of laser parameters on the formation and evolution of micro-cracks were further investigated, and surface characteristics were characterized by using X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). The results showed that under the peak laser power intensity of 2.3 × 1011 W/m2, when increasing the scanning speed from 1 to 5 mm/s, the maximum width of micro-cracks reduced from 3 μm to be less than 1 μm; further increasing to 10 mm/s, no micro-cracks appeared. When increasing the laser power intensity, the micro-groove structure would be formed with pileup around it and line cracks, open cracks and laser pulse tracks on it. During multi-line laser scanning, the pulse overlap rate also affected the formation and distribution of micro-cracks. At last, the formation mechanism of micro-cracks was discussed. These results would be meaningful for understanding the laser-MG interaction as well as guiding the selection of laser parameters for various applications.

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