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Study of the effect of surface laser texture on tribological properties of cemented carbide materials
摘要： Surface texturing has become a potential method to obtain a low friction coefficient under dry/lubricated conditions for different mechanical product surfaces. The mechanism of friction and wear reduction from a micro-texture on the surface of cemented carbide cutting tools was investigated by dry cutting a titanium alloy. Three kinds of micro-textures, namely, line, sinusoidal and rhombic grooves, with different area occupancy rates were produced by a laser on the cemented carbide surface. Experiments and finite element simulation of ABAQUS were used to investigate the tribological characteristics of micro-textured cemented carbide. The results indicated that the line-textured cemented carbide with an area occupancy rate of 10% showed a low friction coefficient of 0.076, which is approximately 34% of the non-textured sample. Few adhesives appeared on the textured surface, while a large number of adhesives were attached to the smooth surface after 30 min of dry friction between the cemented carbide and the titanium alloy balls. Moreover, among the three textures, the line-groove texture has the smallest friction coefficient and a good anti-wear effect. The results show that the existence of a groove texture can effectively reserve the wear debris, reduce the bond wear and weaken the furrow effect.
关键词： titanium alloy,friction and wear,Cemented carbide,machine tool and chip contact zone,surface texture
更新于2025-09-23 15:19:57
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Studies on development of NiTi-integrated optical fiber sensor and its life cycle behavior
摘要： Shape memory alloy coating on an optical fiber plays an important role in developing novel active thermal sensors in the field of microelectromechanical systems. In this article, a detailed analysis of NiTi alloy deposited over plastic optical fiber was discussed. A detailed investigation of the morphological, structural, and thermal properties of the NiTi-coated optic fiber was conducted. The uniformity, crystallinity, transformation temperatures, and thermal stability of the coatings were measured using differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis, respectively. Also, an electrical actuation setup thermo-mechanical test was conducted through Joule heating in which different voltages at varying loads have been used. The sensor characteristic–based parameters (time response and sensitivity) were also calculated. The article presents a complete analysis of experimental results showing the properties and performances of the plastic optical fiber after coating with shape memory alloy.
关键词： shape memory alloy,flash evaporation,Fiber optic sensor
更新于2025-09-23 15:19:57
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Plasma-processed CoSn/RGO nanocomposite: A low-cost and sustainable counter electrode for dye-sensitized solar cells
摘要： The high cost of state-of-the-art Pt counter electrodes (CEs) hinders the large-scale applications of dye-sensitized solar cells (DSCs). The development of Pt-free catalysts while maintaining state-of-the-art catalytic activity for CE materials is one mean to reduce costs. Here, CoxSn1-x/reduced graphene oxide (RGO) (0 ≤ x ≤ 1) nanohybrids were synthesized and employed as inexpensive, stable, and earth-abundant CEs in DSCs. The synthesis was performed through the plasma-assisted reduction of the oxygen functional groups of the graphene oxide along with the immobilization of bimetallic nanoparticles (NPs) on the surface of RGO. The optimization of the composition of the alloy NPs for the highest e?ciency of DSC yields the Co0.9Sn0.1/RGO nanocomposite. The highest device performance correlates well with the experimentally obtained lowest charge transfer resistance in conjunction with the highest electrocatalytic activity of the Co0.9Sn0.1/RGO CE. The DSC employed the synthesized CE showed good stability over long term operation. Both the developed CoSn/RGO nanohybrids and the strategy used for their synthesis are cost-e?ective. Our results provide economically implementable and green nanotechnology for e?cient and stable DSCs required for commercialization.
关键词： Plasma reduction,Bimetalic alloy CoxSn1-x,Nanohybrids,Reduced graphene oxide,Counter electrode,Dye-sensitized solar cells
更新于2025-09-23 15:19:57
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Enhancing Hardness and Wear Performance of Laser Additive Manufactured Ti6Al4V Alloy Through Achieving Ultrafine Microstructure
摘要： Refining microstructure is an important issue for laser additive manufacturing (LAM) of titanium alloy. In the present work, the microstructures of LAM-fabricated Ti6Al4V alloy were refined using a low energy density with the combination of a small spot diameter, a low laser power, and a high scanning speed. The microstructure, hardness, wear performance, and molten pool thermal behavior of LAM-fabricated Ti6Al4V coatings were studied. The results show that the grain sizes of both prior β and α phases are strongly dependent on the cooling rate of the molten pool. The fine prior β grains and submicron-scale acicular α phases were obtained under a low energy density of 75 J mm?2 due to the high cooling rate of the molten pool. In addition, the as-fabricated Ti6Al4V sample with submicron-scale acicular α phase showed a very high hardness of 7.43 GPa, a high elastic modulus of 133.6 GPa, and a low coefficient of friction of 0.48. This work provides a good method for improving the microstructure and mechanical performance of LAM-fabricated Ti6Al4V alloy.
关键词： wear properties,hardness,laser additive manufacturing,titanium alloy,microstructure
更新于2025-09-23 15:19:57
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Laser Welding of ZE41 Mg Alloy: Experimental Investigations on the Effect of Parameters and Nondestructive Testing
摘要： Laser beam welding is an essential metal joining method for magnesium and its alloys with their growing applications in automotive, aerospace, marine, etc. In this research paper, the experimental modelling for laser beam welding of ZE41 Mg alloy and the mechanical and metallurgical characterisation after welding are reported. The effects of weld scan speed and laser beam power on the weld geometry for bead on plates of ZE41 Mg alloy using a continuous-wave CO2 laser system were analysed in this work. The microstructure, hardness, and radiography analysis were discussed. The results indicate the in?uence of laser parameters and the validity of the regression equations developed for the optimisation of process parameters.
关键词： ZE41 magnesium alloy,Hardness,Optimisation,X-ray radiography,Laser beam welding
更新于2025-09-23 15:19:57
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Grain orientation and crystallographic texture governed gradient oxidation in laser peening
摘要： This study examined the microstructural/crystallographic textural changes within a laser peened circular spot on Al-Li alloy 2060-T8 and their correlation with gradient oxidation. These changes were looked at the center and edge regions of the circular spot peened at 8 J and 13 J pulse energies. At the pulse energy of 13 J, grain orientation profoundly changed from h0 0 1i (base region) to h1 1 0i (laser spot) with reduced low coincidence site lattice boundaries at the edge of the laser spot. Ideal fibre texture was transformed into strong Cube {0 0 1} h1 0 0i and Goss {0 1 1} h1 0 0i textures respectively at 8 J and 13 J. Dense atomic structured h1 1 0i and h1 1 1i grain orientations and transformed strong Goss texture are observed to promote the oxidation significantly at the edge of laser spot for 13 J. Reasons for gradient oxidation within the laser peened spot were explained from the view point of microstructural/crystallographic textural changes.
关键词： Al-Li alloy,Oxidation,Grain boundaries,Texture,Laser peening
更新于2025-09-23 15:19:57
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Selective laser melting of Inconel 718 under high laser power
摘要： Selective laser melting (SLM) process has been lately extensively applied in manufacturing of Nickel-based super alloys, which compared to conventional manufacturing routes offers increased design flexibility and simplification of the manufacturing process. However, in order to make SLM process even more beneficial, its process time has to be reduced. One of the ways to tackle this problem is by tailoring process parameters through application of high laser power and base plate pre-heating. In this paper, a comparative study of optimum SLM fabrication conditions of Inconel 718 superalloy under high laser power and with and without plate pre-heating was conducted. Furthermore, the effect of layer thickness on melt pool characteristics, porosity and hardness were investigated to determine how laser power and pre-heating affect microstructure development.
关键词： Additive manufacturing,Texture,Grain structure,Selective laser melting,Nickel alloy
更新于2025-09-23 15:19:57
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Preparation, microstructure, and microhardness of selective laser-melted Wa??3Ta sample
摘要： Tungsten (W) alloy is of difficulty in processing for conventional way because of its high melting point. Here, W alloy sample with the addition of 3 wt% Ta was prepared by selective laser melting. The influence of volumetric energy density (VED) on the surface morphology and the relative density was discussed, and microstructure, phase composition, and microhardness were investigated. The results show that a smooth surface and high relative density (95.79%) can be obtained under optimal VED. The W–Ta substitutional solid solution formed because of the replacement of Ta atom. There are strip and block fine grains in the W–3Ta sample with no significant texture. In addition, subgrain structure with a size of around 1 lm formed inside the strip grain, owing to the large thermal gradient and extremely fast cooling rate. Finally, the W–3Ta alloy shows higher microhardness than that obtained by traditional methods.
关键词： tungsten alloy,volumetric energy density,microstructure,microhardness,selective laser melting
更新于2025-09-23 15:19:57
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Precise laser trimming of alloy strip resistor: A comparative study with femtosecond laser and nanosecond laser
摘要： Laser trimming has become one of the powerful tools for precise manufacturing of alloy resistors that are widely used in electrical vehicles, electrical controlling, and in appliances. In this work, the influence of femtosecond laser trimming is compared with nanosecond laser trimming. The authors found that lasers focused on different heights relative to the sample surface induced significant changes in surface morphologies. The resistance change was systematically investigated as a function of cutting lengths and cutting depths of different laser powers for both lasers. The experiments display that femtosecond laser trimming has a higher precision of the resistance adjustment than nanosecond laser trimming. The periodic ripple structure by the femtosecond laser was investigated at the focus position above, onto, or beneath the surface. The period of a low frequency ripple structure (LFRS) on the ablated groove bottom is about 600–700 nm when the laser focuses just right on the surface but changes to 490–560 nm when focusing above or beneath the surface. The period of a high frequency ripple structure is about 100–380 nm at the vertical direction of LFRS. The period of low frequency ripple on the outside of the groove is smaller than that on the groove bottom for all three focusing cases. The period of the LFRS is not sensitive to the laser power. The range of the resistor value change in the s-polarized light direction of the femtosecond laser is more than that in the p-polarized light direction.
关键词： Fe-Cr-Al alloy resistor,micromachining,femtosecond laser trimming,nanosecond laser trimming
更新于2025-09-23 15:19:57
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Microstructure Influence of SACX0307-TiO2 Composite Solder Joints on Thermal Properties of Power LED Assemblies
摘要： The effect of the microstructure of solder joints on the thermal properties of power LEDs is investigated. Solder joints were prepared with different solder pastes, namely 99Sn0.3Ag0.7Cu (as reference solder) and reinforced 99Sn0.3Ag0.7Cu–TiO2 (composite solder). TiO2 ceramic was used at 1 wt.% and with two different primary particle sizes, which were 20 nm (nano) and 200 nm (submicron). The thermal resistance, the electric thermal resistance, and the luminous efficiency of the power LED assemblies were measured. Furthermore, the microstructure of the different solder joints was analyzed on the basis of cross-sections using scanning electron and optical microscopy. It was found that the addition of submicron TiO2 decreased the thermal and electric thermal resistances of the light sources by 20% and 16%, respectively, and it slightly increased the luminous efficiency. Microstructural evaluations showed that the TiO2 particles were incorporated at the Sn grain boundaries and at the interface of the intermetallic layer and the solder bulk. This caused considerable refinement of the Sn grain structure. The precipitated TiO2 particles at the bottom of the solder joint changed the thermodynamics of Cu6Sn5 formation and enhanced the spalling of intermetallic grain to solder bulk, which resulted in a general decrease in the thickness of the intermetallic layer. These phenomena improved the heat paths in the composite solder joints, and resulted in better thermal and electrical properties of power LED assemblies. However, the TiO2 nanoparticles could also cause considerable local IMC (Intermetallic Compounds) growth, which could inhibit thermal and electrical improvements.
关键词： power LED,SAC composite alloy,TiO2 ceramic,luminous efficiency,thermal resistance,microstructure characterization
更新于2025-09-23 15:19:57