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Porosity and joint property of laser-MIG hybrid welding joints for 304 stainless steel
摘要： Laser-metal inert gas (MIG) hybrid butt welding was carried out on 5 mm-thick 304 stainless steel to study the influence of parameters on porosity defect, weld formation, and property of the joints. Research reveals that laser-MIG hybrid welding of 304 stainless steel has porosity sensitivity. The effects of welding speed and laser power on porosity and formation of welds were analyzed. Results show that increasing of laser power and decreasing of welding speed are conducive to improve the formation of welds and reduce porosity. Improving the welding speed on the premise of ensuring proper weld formation is of considerable significance, which is recommended to be 1.8 m/min. Based on the fixed welding speed, parameter of laser power optimization is carried out. Results show that tensile strength and elongation of the welded joints reach at least 98.1% and 75.8% of the base metal when laser powers are 4.3 and 5.0 kW. Compared with real-time monitoring and the numerical simulation method, this kind of results-oriented optimization parameter method has engineering guiding significance.
关键词： property,welding parameter,weld formation,304 stainless steel,porosity,laser-MIG hybrid weld
更新于2025-09-23 15:21:01
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Small fatigue crack growth behavior of Ti-6Al-4V produced via selective laser melting: In situ characterization of a 3D crack tip interactions with defects
摘要： Small fatigue crack growth (SFCG) behavior is examined for additively manufactured Ti-6Al-4V specimens with optimal and trial build conditions (representing an increased degree of defects) through a combination of in situ tomography and in situ energy dispersive X-ray diffraction. The results showed slower crack growth rates for the SFCG samples compared to the long cracks (which was not expected). In the case of the trial conditions, the increased levels of porosity deterred crack growth by blunting the crack, as evident by the in situ tomography characterization.
关键词： In situ tomography,Porosity,Energy dispersive X-ray diffraction,Process build conditions,Additive manufacturing
更新于2025-09-23 15:21:01
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Laser Heat Treatment of Ferrocarbon Powder Steel
摘要： The laser heat treatment of sintered ZhGr ferrocarbon powder steel with different porosity is considered. The microstructure and microhardness of the steel are determined, and the defects arising in laser treatment are studied.
关键词： microhardness,ferrocarbon steel,porosity,laser heat treatment,powder metallurgy,microstructure
更新于2025-09-23 15:19:57
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Role of thermal fluid dynamics in alloying element distribution and weld porosity in powder feeding-based laser welding of Al alloy
摘要： This work develops a model incorporating the powder transport, laser heating, and molten pool dynamics to describe the mixing process of alloying element and reveal the mechanisms of bubble dynamics in powder feeding-based laser welding. Simulation results show that the different roles of recoil pressure: driving the molten metal flow at the rear part of keyhole in partial penetration and maintaining the stable keyhole profile in full penetration, are responsible for the difference between their melt flow behaviors. Driven by the melt flow, the alloying element transport path can be generalized as the shallow areas, the rear areas, the central and bottom areas in partial penetration. It permits a relatively uniform silicon distribution. However, two vortices rotating in the opposite direction in full penetration results in a higher concentration of Si in the upper part. Meanwhile, we conclude three steps for the bubble dynamics: bulge formation, bubble formation, bubble being captured by re-formed keyhole or being captured by the solid-liquid interface or escaping from the free surface. Such phenomena manifest that the contributions to the processing quality and metallurgy quality of welded joints come from the complex melt flow behaviors, which are confirmed by a series of experiments.
关键词： Thermal fluid dynamics,Alloying element distribution,Melt flow,Powder feeding-based laser welding,Weld porosity
更新于2025-09-23 15:19:57
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Laser Optoacoustic Method for Quantitative Porosity Assessment of Carbon Fiber Reinforced Plastic Composites Based on Acoustic Impedance Measurement
摘要： A method for measuring the acoustic impedance for the assessment of the porosity of carbon fiber reinforced plastic composites using laser thermo-optical excitation of longitudinal acoustic waves is proposed and experimentally realized. The acoustic impedance of the test sample is measured from the magnitude of the antiderivative ultrasonic pulse reflected from the immersion liquid–sample interface. A method for calculating the porosity of carbon fiber plastic composites based on the measured acoustic impedance is presented. Composite samples with three different carbon fiber layers stacking schemes were investigated. It is shown that in the studied composites, the local porosity distribution is nonuniform along the fiber stacking plane. The porosity value, averaged from optoacoustic measurement results, actually coincides with X-ray tomography data within the error limits. The presented method for determining porosity does not require determining the volume and mass of the studied object and can be used for investigation of composite structures with complex shapes.
关键词： porosity,laser optoacoustic method,polymer composites,longitudinal acoustic waves
更新于2025-09-23 15:19:57
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Laser-assisted glass-based sealing of polished porcelain stoneware tile surface to increase stain resistance
摘要： This study aims to develop a new approach for the permanent sealing of surface pores on polished porcelain stoneware tiles, using ceramic frits for the filling pores, followed by laser-sealing to ensure the fixation of the applied material. The laser-sealing parameters compatible with the ceramic substrate were focus height (z) of 105 mm, scan speed (v) of 2640 mm.min-1, and power values of 750, 800, and 850 W. In order to define the working parameters, three ceramic frits with 30, 50, and 70 wt.% solid contents were tested by sealing at the mentioned powers. High stain resistant polished stoneware tiles were obtained using frit 1 and frit 3 with 50 and 70 wt.% solid contents, respectively, and the proposed procedure. High ease of cleaning is obtained related to the current treatment, demonstrating its suitability for improving the stain resistance for meeting the ISO 13006:2012 requirements.
关键词： Ceramic frits. Laser Processing. Porcelain Tile. Porosity. Stain Resistance.
更新于2025-09-23 15:19:57
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Low-Loss and Dispersion-Flattened Octagonal Porous Core PCF for Terahertz Transmission Applications
摘要： In order to make the direct transmission more effective, we have intended an octagonal shape cladding design in this paper. The minimum resultant effective material loss obtained from our proposed photonic crystal fiber is 0.007 cm-1 at 0.5 THz is very effective. The proposed design gives an ultra-high birefringence of 0.06 with an effective area of about 4 9 10-6 m2, a core power fraction of 70% for 290 lm core diameter with a core porosity of 80% at 1.6 THz frequency and closely zero flattened dispersion of variation of 0.3 ± 0.1 ps/THz/cm at a wide frequency range of 0.7–2.1 THz.
关键词： Terahertz,Core porosity,Effective material loss,Octagonal core,Confinement loss,Dispersion
更新于2025-09-23 15:19:57
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Generation of graded porous structures by control of process parameters in the selective laser melting of a fixed ratio salt-metal feedstock
摘要： The demonstration of salt dissolution incorporated within laser powder-bed fusion fabrication processes has allowed the creation of complex porous structures without the need for sophisticated design algorithms. This serves to simplify the process, for porous structure creation in powder-bed fabrication techniques, creating a new opportunity for the realisation of optimised structures. A new methodology is presented here in which modulation of the energy density while using a single feedstock material enables three-dimensional control of porosity, ranging from 20 % to 49 %. Through structured experimentation, the response of the material to varying the process parameters in selective laser melting is evaluated and nested structures of distinct densities and morphologies are created. Correlation of the process parameters with modulus and ultimate compressive stress are established. A simple-assembly algorithm was used to generate complex parts consisting of locally assigned porosities having characteristic properties.
关键词： Selective laser melting,Graded materials,Mechanical performance,Controlled-porosity,Additive manufacturing,Cellular structures,Porous
更新于2025-09-23 15:19:57
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Numerical prediction of solid-liquid front during laser melting of fused quartz
摘要： A 2-D transient model is explored for knowing the process of melting with laser in a Fused Quartz work piece. The work piece is irradiated with a single Gaussian laser pulse. The temporal variation is trapezoidal in nature. The laser source is considered as volumetric instead of surface laser source to match more closely with experiment. The convection and radiation heat losses are considered from the irradiated surface. By using the FVM (Finite Volume Method), the energy equation is discretized. The resulting algebraic equation is explained with the help of Tridiagonal matrix algorithm (TDMA) and it is to find the temperature field in the work piece. To capture the solid liquid front during the melting process the enthalpy-porosity method is used. With the help of available experimental results, the temperature field obtained is validated and a good agreement is found. The temperature field, the progress of the solid liquid front at different heating times and the melt depth is analysed to control the melting with laser intensity value.
关键词： Laser pulse,TDMA,Laser,Finite volume method,Enthalpy-porosity,Melting
更新于2025-09-23 15:19:57
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Innovative in situ photocuring-assisted 3D plotting technique for complex-shaped ceramic architectures with high shape retention
摘要： We herein propose a novel type of additive manufacturing (AM) technique, denoted as "in situ photocuring-assisted 3D plotting", which can rapidly solidify extruded green filaments comprised of ceramic powders and photocurable monomers using UV light during 3D plotting. To accomplish this, the rheological properties and photocuring behavior of the ceramic slurry were carefully tailored, particularly by using a mixture of diruethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate (TEGDMA) monomers as the photocurable vehicle. This innovative approach enabled the favorable extrusion of the ceramic slurry through a fine nozzle with high green strength after photocuring, and thus complex-shaped ceramic architectures with high shape retention could be constructed. As an example, a free-standing helical structure with a circular cross-section was successfully produced even without the use of any supporting materials. In addition, a porous ceramic scaffold with a tightly controlled porous structure could be produced.
关键词： Strength,Porosity,Extrusion,Structural applications,Suspensions
更新于2025-09-19 17:15:36