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Journal of Laser Applications
Journal Prestige (SJR): 0.741  Citation Impact (citeScore): 2 Number of Followers: 14  Subscription journalISSN (Print) 1042-346X Published by AIP  [28 journals]
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- Review: Laser shock processing technique on the additive manufactured
metallic alloys-
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First page: 031201
Abstract: Additive manufacturing (AM) is an efficient method to fabricate components with complex geometries. However, high levels of tensile residual stress generated in the near-surface layer of the fabricated components due to the high cooling rate and large thermal gradients during the AM process have limited their applications. Laser shock processing (LSP) is a novel surface-strengthening technique applied to modify the near-surface of metallic materials with the purpose of improving mechanical properties such as microhardness, residual stress, wear resistance, and fatigue performance. There are more and more investigations to report the combining manufacturing process of metallic alloys through AM and LSP. In this perspective, the fundamental mechanisms of AM and LSP were summarized in detail. The combining manufacturing process with LSP and AM was introduced from the aspect of residual stress, microhardness, fatigue performance, wear resistance, and microstructure evolution. Also, the microstructure-property relationship was discussed to explain the strengthening mechanism of AMed components by LSP. This work has important reference value and guidance significance for researchers to widespread the accepted LSP as a postprocessing method in the fields of AM.
PubDate: Thu, 08 Aug 2024 00:00:00 GMT
DOI: 10.2351/7.0001411
Issue No: Vol. 36, No. 3 (2024)
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- Research on a visual positioning method of paddy field weeding wheels
based on laser rangefinder-camera calibration-
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First page: 032001
Abstract: The positioning of paddy field weeding wheels is of great significance for compensating the operation deviation between the weeding wheel and the seedling row in paddy field mechanical weeding. In this paper, a visual positioning method for determining the three-dimensional coordinates of weeding wheels in the camera coordinate system is proposed. By fixing the laser rangefinder with the weeding wheel, the proposed method converts the positioning of weeding wheels into solving the relative pose relationship between the laser rangefinder and the camera. Then, based on the constraints of the laser spots on the AprilTag calibration plane, a nonlinear optimization model is established to obtain the relative pose parameters. In the experiment, two evaluation indicators were proposed to evaluate the calibration accuracy. The experimental results showed that the proposed visual positioning method of the weeding wheel can reach a mean positioning error of 2.766 mm and a mean pixel error of 7.161 pixels.
PubDate: Mon, 03 Jun 2024 00:00:00 GMT
DOI: 10.2351/7.0001341
Issue No: Vol. 36, No. 3 (2024)
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- Construction of microstructures on the Cu substrate using ultrafast laser
processing to enhance the bonding strength of sintered Ag nanoparticles-
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First page: 032002
Abstract: Silver nanoparticle (Ag NP) pastes become a potential die-attachment material with the increased electronic power density. However, the weakness of bonding interface between sintered Ag NPs and bare Cu substrate limits the applications of the Ag NPs paste, thereby reducing the shear strength of the sintered joint. In this work, ultrafast laser processing is utilized to enhance the bonding strength of the sintered Ag joint by fabricating a microstructure interface. The microstructure dimensions are tunable by controlling laser parameters, and then high-strength joints could be obtained. Different substrate microstructures were constructed, and the enhanced bonding mechanism was analyzed by characterizing the cross section and fracture surface morphologies of joints. The ultrafast laser processing could increase the surface energy of Cu substrates to form a more reliable connection with Ag NPs and more energy required for crack extension with the increasing connection area, thereby resulting in a significant improvement in the shear strength of the Ag NP joints. The patterned microstructures on the Cu substrate using this technique showed improved surface energy and increased number of connection areas on the substrate, showing potential for the use in third-generation semiconductors for highly reliable packaging.
PubDate: Wed, 05 Jun 2024 00:00:00 GMT
DOI: 10.2351/7.0001327
Issue No: Vol. 36, No. 3 (2024)
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- Microstructure and corrosion of SLM IN718 in 3.5% NaCl solution at high
temperatures-
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First page: 032003
Abstract: This study investigated the temperature dependence of IN718 corrosion behavior in 3.5 wt. % NaCl solution, comparing conventionally rolled (Roll) and SLM-manufactured (SLM) samples. While both exhibited degradation with increasing temperature, the Roll sample presented a significantly higher susceptibility to corrosion by increasing the temperature from 25 to 70 °C. Rapid corrosion current density (icorr) of the Roll sample, which increased from 0.25 to 1.3 μA cm2, suggested the preferential γ-matrix dissolution and microgalvanic attack triggered by Laves phases and carbides acting as preferential dissolution sites. Conversely, the SLM sample showcased less segregation and fewer carbide phases due to its high cooling rate, resulting in a milder icorr rise (0.45–0.6 μA cm2). The findings hold promise for a more comprehensive understanding of IN718 performance and can guide the selection of optimal fabrication methods for components exposed to corrosive and high-temperature environments.
PubDate: Thu, 06 Jun 2024 00:00:00 GMT
DOI: 10.2351/7.0001379
Issue No: Vol. 36, No. 3 (2024)
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- Numerical simulation of thermal evolution and grain morphology of laser
melted AlSiTiNiCo-WC composite coatings-
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First page: 032004
Abstract: Simulation of the geometry and internal grain size changes of laser cladding has been extensively studied, with the majority of such simulations focusing on pure metal powders. However, there are fewer simulations for aluminum-based composite coatings by laser cladding. In this paper, a new three-dimensional model of laser cladding composite coatings is proposed, which can accurately determine the geometrical size of the AlSiTiNiCo-WC cladding layer and the internal grain morphology and grain size changes of the cladding layer. The temperature-selective judgment mechanism and material thermal property calculation ensure the calculation accuracy of the composite coating, while the model accurately and intuitively determines the state changes of the composite coating in the process of laser cladding. Furthermore, the model verifies the feasibility of the exponential decay laser source in the simulation of composite cladding, and temperature field analysis accurately predicts the trends of grain morphology and grain size inside the cladding. The simulation results show that the variation of the laser scanning speed has a more pronounced effect on the depth of the cladding layer. The high-temperature gradient at the top of the molten pool is more likely to form fine grains, and the bottom of the cladding layer tends to form coarse columnar crystals with the increase in the internal temperature gradient at the depth. The simulation results were compared with experimental results to validate the accuracy of the simulation process.
PubDate: Fri, 07 Jun 2024 00:00:00 GMT
DOI: 10.2351/7.0001278
Issue No: Vol. 36, No. 3 (2024)
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- Effects of laser power on microstructure and mechanical properties of
titanium alloy fabricated by laser-arc hybrid additive manufacturing-
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First page: 032005
Abstract: Laser-arc hybrid additive manufacturing (LAHAM) based on the synergistic interaction of laser and arc has vast potential applications due to the advantages of high precision and fast manufacturing speed. Titanium alloy is a kind of indispensable material in the aerospace and marine industries because of its superior performance. This study primarily investigates the effect of laser power on formability, microstructure evolution, and mechanical properties of Ti-6Al-4V, a titanium alloy fabricated by LAHAM. The results indicate that the material utilization of the Ti-6Al-4V wire first increases and then decreases with the increasing laser power, reaching a maximum value of 95.48% at a power of 1500 W. As laser power increases, the acicular martensite α′ content in the LAHAM samples decreases, while the α phase increases and exhibits a coarsening phenomenon. Tensile strength increases with the rise in laser power, reaching a maximum horizontal tensile strength of 1080 MPa and a maximum vertical tensile strength of 1100 MPa. However, elongation decreases with increasing laser power. Microhardness decreases with the rise in laser power. The increase in laser power enhances the bonding between deposition layers, significantly improving the tensile strength of the specimens.
PubDate: Wed, 12 Jun 2024 00:00:00 GMT
DOI: 10.2351/7.0001344
Issue No: Vol. 36, No. 3 (2024)
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- High-accuracy predictive model for carbon fiber reinforced polymer laser
machining quality using neural networks-
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First page: 032006
Abstract: In order to address the issue of thermal damage induced by laser processing of carbon fiber reinforced polymer (CFRP), researchers have conducted an optimization study of process parameters in the laser processing of CFRP. Their aim is to elucidate the relationship between process parameters and processing quality to minimize thermal damage. However, during laser processing, there exists a complex nonlinear relationship between process parameters and processing quality, making it challenging to establish high-precision predictive models, while the intrinsic connection between these two aspects remains incompletely revealed. In light of this, this study proposes utilization of machine learning techniques to explore the inherent relationship between process parameters and processing quality and establishes a 5-13-5 type back-propagation (BP) neural network predictive model. Subsequently, genetic algorithms are employed to optimize the weights and thresholds of the BP neural network, and the model is then subjected to validation. The results indicate that the BP neural network predictive model yields average errors of 5% for surface heat-affected zone (HAZ), 2.9% for groove width, 5.9% for cross-sectional HAZ, 1.8% for groove depth, and 4.5% for aspect ratio, demonstrating a relatively high level of accuracy but with notable fluctuations. The GA-BP model, when predicting the surface HAZ and the groove width, achieves errors of 4.5% and 2.7%, respectively, which are lower when compared to the BP model, indicating a higher predictive accuracy. The GA-BP model established in this study unveils the intrinsic connection between process parameters and processing quality, providing a novel means for an effective quality prediction in the processing of CFRP.
PubDate: Thu, 13 Jun 2024 00:00:00 GMT
DOI: 10.2351/7.0001313
Issue No: Vol. 36, No. 3 (2024)
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- Femtosecond laser etching of Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 glass using
the Bessel beam-
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First page: 032007
Abstract: Surface textured materials can exhibit enhanced properties due to their unique morphology, large surface area, and modified surface properties. The laser etching process has garnered significant attention for its capability to create textures on sample surfaces, resulting in a substantial improvement of surface properties. In this study, we investigate the application of femtosecond laser etching on solid electrolytes. To achieve this, an axicon lens is employed to transform the conventional Gaussian beam into a Bessel beam, with an extended focal depth that facilitates the laser etching process. A telescope laser system with a Bessel beam having a focal length of 2 mm is constructed based on finite element analysis. Glassy LAGP [Li1.5Al0.5Ge1.5(PO4)3] with a thickness of 2 mm is successfully etched simultaneously on both surfaces using this approach. Utilization of femtosecond laser pulses effectively prevents sample melting during the process. As predicted by finite element analysis, wider ditches are observed on the surface compared to those on the backside due to higher laser intensity at the surface region. By modifying the parameters of the telescope laser system, size and depth control can be achieved for these ditches.
PubDate: Thu, 13 Jun 2024 00:00:00 GMT
DOI: 10.2351/7.0001274
Issue No: Vol. 36, No. 3 (2024)
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- Synthesis of bimetallic core/shell nanoparticles via pulse laser ablation
and their catalytic effectiveness in dye degradation-
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First page: 032008
Abstract: In this study, a simple two step method is employed to sequentially synthesize bimetallic core/shell nanoparticles (NPs). In the first step, pure mono Au and Ag NPs are prepared via 1064 nm pulsed laser ablations in liquid. In the second step, the Au/Ag substrate immersed in the Au/Ag colloidal solution is exposed to the nanosecond laser at 1064 nm wavelength using various laser energies and ablation periods. The crystalline phase and morphology of the bimetallic core/shell NPs (Au/Ag, Ag/Au) are examined by x-ray diffraction and scanning electron microscopy, respectively. The results showed that highly crystalline, well-dispersed spherical monometallic and bimetallic core/shell NPs can be synthesized via pulse laser ablation in liquid. The average diameter of Au, Ag, Au/Ag, and Ag/Au NPs is 34, 40, 58, and 43 nm, respectively. With increasing laser energy, the plasmonic absorption peak of Au NPs redshifts and that of Ag NPs blueshifts. For core/shell, two plasmonic peaks were observed, each of which shifted with increasing ablation time for shell material. Organic dyes with concentrations of 10 − 5 M of methylene-blue with NaBH 4 of 0.05M and methylene-orange with NaBH 4 of 0.1M are used to examine the catalytic performance of the NPs. The core/shell NPs performed better than monometallic NPs. In particular, the catalytic degradation efficiency of Au/Ag and Ag/Au NPs is approximately 90% in significantly less time than monometallic Au and Ag NPs.
PubDate: Thu, 13 Jun 2024 00:00:00 GMT
DOI: 10.2351/7.0001347
Issue No: Vol. 36, No. 3 (2024)
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- Random lasing using laser generated and modified silver nanoparticles
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First page: 032009
Abstract: The authors report incoherent random laser action in systems where the optical feedback is provided by multiple scattering generated by different classes of silver nanoparticles in the colloidal state, having plasmon resonances at different frequencies. They found improved performance of triangular silver nanoplates as compared to nanospheres, with a threshold as low as 1 mJ/cm2 and a 5 times lower optimal silver concentration, due to plasmonic enhancement effects and tuning of the plasmon resonance. The nanoparticles were also tested for stability against illumination by the pump laser, as the onset of pulsed laser melting is comparable to random laser threshold in terms of pump fluence, severely limiting the range of operation of nanoparticles with main plasmon resonance close to the pump wavelength. The optimal approach to choose plasmonic nanoparticles for random lasing must, therefore, take the stability aspect into serious consideration as well as the plasmonic enhancement of random lasing.
PubDate: Mon, 17 Jun 2024 00:00:00 GMT
DOI: 10.2351/7.0001412
Issue No: Vol. 36, No. 3 (2024)
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- CFD modeling for predicting imperfections in laser welding and additive
manufacturing of aluminum alloys-
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First page: 032010
Abstract: Aluminum and its alloys are widely used in various applications including e-mobility applications due to their lightweight nature, high corrosion resistance, good electrical conductivity, and excellent processability such as extrusion and forming. However, aluminum and its alloys are difficult to process with a laser beam due to their high thermal conductivity and reflectivity. In this article, the two most used laser processes, i.e., laser welding and laser powder bed fusion (LPBF) additive manufacturing, for processing of aluminum have been studied. There are many common laser-material interaction mechanisms and challenges between the two processes. Deep keyhole mode is a preferred method for welding due to improved productivity, while a heat conduction mode is preferred in LPBF aiming for zero-defect parts. In LPBF, the processing maps are highly desirable to be constructed, which shows the transition zone. Presented numerical modeling provides a more in-depth understanding of porosity formation, and different laser beam movement paths have been tested including circular oscillation paths. High accuracy processing maps can be constructed for LPBF that allows us to minimize tedious and time-consuming experiments. As a result, a modeling framework is a highly viable option for the cost-efficient optimization of process parameters.
PubDate: Mon, 01 Jul 2024 00:00:00 GMT
DOI: 10.2351/7.0001401
Issue No: Vol. 36, No. 3 (2024)
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- Active control effect of shielding gas flow on high-power fiber laser
welding plume-
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First page: 032011
Abstract: Plume are common physical phenomena in fiber laser keyhole welding and have serious negative effects on the welding process. Based on this, this paper explores the regulation law of conventional shielding gas flow on plume. The results show that the shielding gas has a very significant effect on the suppression of the slender part of the plume, and the greater the gas flow rate, the better the plume removal effect. The addition of the shielding gas makes the welding process more stable, the molten pool flows stably, and the frequency of spatter eruption is reduced. Under the experimental conditions, the optimal shielding gas flow rate is around 15 l/min, and the penetration depth and width are increased by about 10% and decreased by about 22%, respectively, compared with that without adding the shielding gas. Based on the gas flow simulation, the gas flow pressure (about 132 Pa) generated by an appropriate amount of shielding gas (about 15 l/min) can press the liquid column and spatter near the keyhole mouth into the molten pool to avoid the spatter eruption. Excessive shielding gas flow will interfere with the flow of the molten pool excessively, and the weld surface will show a serious undercut phenomenon.
PubDate: Mon, 08 Jul 2024 00:00:00 GMT
DOI: 10.2351/7.0001407
Issue No: Vol. 36, No. 3 (2024)
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- Prediction and optimization of joint quality in laser transmission welding
using serial artificial neural networks and their integration with Markov
decision process-
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First page: 032012
Abstract: Laser transmission welding is a highly accurate method for joining plastics, but its diverse process parameters require effective modeling for optimal results. Traditional artificial neural networks (ANNs) typically establish predictive models between laser processing parameters and welding strength, neglecting the crucial role of welding morphology in feature extraction, thus diminishing accuracy. To address this, we developed a serial ANN model based on statistically evident correlations, which predicts joint morphology and strength sequentially, resulting in a 47% improvement in predictive accuracy and a mean error of just 7.13%. This two-layered approach effectively reduces the stepwise propagation of errors in ANNs, allowing the first layer to provide a refined data representation for the second layer to predict welding strength. Furthermore, finding the optimal laser parameter set is time-consuming and computationally demanding with traditional ANN-based optimization methods. To address this, we integrated the Markov decision process with the serial ANN for the first time and proposed a novel varying step strategy for the model, enabling a balance of swift convergence and avoidance of suboptimal solutions. Notably, the Markov-serial ANN model attained enhanced optimization results using only 15.5% of the computational resources required by a standard parameter interval optimization methodology. Welding experiments verified the reliability of the Markov-serial ANN, achieving a mean error of 4.54% for welding strength.
PubDate: Tue, 09 Jul 2024 00:00:00 GMT
DOI: 10.2351/7.0001384
Issue No: Vol. 36, No. 3 (2024)
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- Comparison of laser induced corneal injury thresholds with safety limits
for the wavelength range of 1200–1500 nm-
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First page: 032013
Abstract: A computer model predicting thresholds for laser induced corneal injury was used to systematically analyze wavelength, pulse duration, and beam diameter dependencies for wavelengths between 1200 and 1500 nm, for the exposure duration regime of 10 μs to 100 s. The thresholds were compared with the maximum permissible exposure (MPE) values to protect the cornea as specified in ANSI Z136.1-2022, ICNIRP 2013, and IEC 60825-1:2014. In the wavelength range between 1200 and 1400 nm, the dominant hazard transitions from the retina to the cornea. Consequently, limits are needed to protect both the cornea and the retina. In the lower wavelength range, the retinal limits are more conservative, while in the higher wavelength range, the corneal limits are lower. Comparison with injury thresholds shows that ANSI MPEs include a large safety margin for all wavelengths. Due to the 7 mm aperture stop defined in IEC 60825-1, levels permitted by the Class 3B limit exceed the predicted injury thresholds for small beam diameters and wavelengths between approximately 1350 and 1400 nm. The Class 3B limit does not appear to be sufficiently protective for these conditions. For skin MPEs, the margin between corneal injury thresholds and MPEs decreases steadily for wavelengths approaching 1400 nm. However, normal eye movements can be expected to reduce the effective exposure so that skin MPEs may serve as adequate limits to protect the cornea for wavelengths less than 1400 nm until a specific limit to protect the cornea is promulgated by ICNIRP.
PubDate: Fri, 12 Jul 2024 00:00:00 GMT
DOI: 10.2351/7.0001375
Issue No: Vol. 36, No. 3 (2024)
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- Prediction of interface width in overlap joint configuration for laser
welding of aluminum alloy using sensors-
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First page: 032014
Abstract: We present a method that can predict the interface width in an overlapping joint configuration for laser welding of Al alloys using sensors and a convolutional neural network (CNN)-based deep-learning model. The inputs for multi-input CNN-based deep-learning prediction models are spectral signals, represented by the light intensity measured by a spectrometer and dynamic images of the molten pool filmed by a charge-coupled device (CCD) camera. The interface width, used as learning data for modeling, was constructed as a database along with the process signal by cross-sectional analysis. In this study, we present results showing high accuracy in predicting the interface width in the overlap joint configuration for Al alloy laser welding. For predicting the interface width, five models are created and compared: a single CCD and spectrometer sensor algorithm, a multi-sensor algorithm with two input variables (CCD, spectrometer), a multi-sensor algorithm excluding the processing beam in the spectrometer data on the combination of Al 6014-T4 (top)/Al 6014-T4 (bottom), and a multi-sensor algorithm applied to the combination of Al 6014-T4 (top)/Al 5052-H32 (bottom). The multi-sensor algorithm with two input variables (CCD and spectrometer) on the same material combination showed the highest accuracy among the models.
PubDate: Fri, 12 Jul 2024 00:00:00 GMT
DOI: 10.2351/7.0001367
Issue No: Vol. 36, No. 3 (2024)
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- Microstructure and dynamic fracture behaviors of laser-MAG hybrid welded
T-joints of 945 shipbuilding steel with different heat inputs-
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First page: 032015
Abstract: Welded T-joints of 945 shipbuilding steel are widely used in plate-beam connections, and their impact toughness directly affects the service life of shipboard structural components. However, current research efforts have primarily focused on the static mechanical properties of welded T-joints, with few scholars investigating the impact properties of welded T-joints under dynamic loading conditions. In this paper, laser-MAG hybrid welding of 945 shipbuilding steel T-joints is utilized to study the effects of heat input on the microstructure evolution and dynamic mechanical properties of welded T-joints. The results show that the increase in heat input results in a decrease in the cooling rate, which promotes the formation of lath martensite in weld metal and the formation of granular and lath bainite in coarse grain heat affected zone (HAZ). Concurrently, the higher heat input increases the width of the HAZ and leads to grain coarsening, resulting in a 298.9% increase in average grain area when the heat input rises from 12.1 to 14.6 kJ/cm. The changes in martensite content and morphology result in a reduction in the microhardness of welded T-joints. The HAZ becomes the most vulnerable region to dynamic impact loading, and the higher heat input leads to ductile fracture. Compared to high heat input, the drop hammer acceleration decreases by 34.0%, the maximum displacement increases by 45.9%, and the fracture energy increases by 43.1%, for low heat input. The changes in the drop hammer impact metrics further illustrate that welded T-joints with lower heat input are favorable for improving impact toughness.
PubDate: Fri, 12 Jul 2024 00:00:00 GMT
DOI: 10.2351/7.0001397
Issue No: Vol. 36, No. 3 (2024)
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- Research on twin method of transient temperature field in laser additive
manufacturing based on optimization of measured parameters-
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First page: 032016
Abstract: The transient temperature field during laser-directed energy deposition has a crucial impact on the quality of manufactured parts. In this study, in order to solve the problems that the transient temperature field is difficult to measure directly and the traditional numerical simulation data are not real time and the model is inaccurate, a transient temperature field twin method based on the optimization of measured parameters is proposed. First, based on heat transfer, a twin model of temperature-dependent thermophysical parameter fluctuations is built, and the model defines the time-dependent power parameters. In order to perform numerical simulations for the acquisition of the temperature field distribution and to verify the accuracy of the model through the comparison of synchronized lateral validation experiments, an integrated measurement-validation experimental system is constructed. A twin model validation method is proposed, in which the frontal measurement experiments are synchronized with the lateral validation experiments. The real-time radius of the molten pool and temperature parameters are extracted from the frontal measurement experiments and inputted into the twin model. In order to confirm the great realism of the built twin model, the simulation of the twin temperature field under various laser strengths is examined in the last step. The experimental findings demonstrate that the temperature field twin physical model developed in this work is capable of faithfully simulating temperature field variations brought about by real-time laser additive process parameter changes. This approach reduces the number and expense of actual tests, helps to adjust process parameters to ensure an improvement in product quality and performance, and makes up for the lack of real-time problems in traditional numerical simulation. It also improves the accuracy and real-time simulation model. Finally, it has the ability to instantly provide input and track the production process in real time. It helps to advance the application of digital-twin technology in the field of additive manufacturing.
PubDate: Fri, 12 Jul 2024 00:00:00 GMT
DOI: 10.2351/7.0001383
Issue No: Vol. 36, No. 3 (2024)
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- New method for high-efficiency keyhole-based wire direct energy
deposition: Process innovation and characterization-
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First page: 032017
Abstract: Wire laser direct energy deposition enables the mass production of large-scale industrial components and parts. However, energy utilization efficiency is limited in conventional wire laser material deposition to avoid keyhole defects, resulting in a low deposition efficiency. This work presents a high-efficiency wire laser material deposition process that increases energy utilization by generating a keyhole in the filler wire, which can also avoid the keyhole defects in the deposited sample. The influence of process parameters on deposition quality and efficiency was thoroughly examined to determine the process window. A high deposition efficiency of 0.87 kg/(h kW) for 316L stainless steel was achieved with a laser power of 3 kW, approximately three times that of the conventional wire laser material deposition process. The defect-free multitrack and multilayer deposition demonstrated the feasibility of our proposed high-efficiency process.
PubDate: Wed, 17 Jul 2024 00:00:00 GMT
DOI: 10.2351/7.0001388
Issue No: Vol. 36, No. 3 (2024)
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- Effect of brazing process on microstructure evolution and mechanical
properties of Ti6Al4V/ZrO 2 joints after laser surface treatment-
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First page: 032018
Abstract: Ti6Al4V alloy and ZrO2 ceramic have similar application fields and complementary properties. Brazing connections can broaden the application range. When using sealing glass with good air tightness, good electrical insulation, and low connection temperature to connect, the solder is difficult to wet on the metal surface. The traditional method is to oxidize the surface of the alloy at a high temperature, but the film is not uniform and the treatment time is long. In this study, nanosecond laser surface treatment was used as a prewelding pretreatment method to form a micro-nano structure on the surface and perform oxidation treatment. It is particularly important to select the brazing process. After the laser parameters and processing times were determined, the effects of different welding temperatures and holding times on the properties of the joints were compared, and it was found that there were regular changes. Finally, it is concluded that the maximum shear strength is 46 MPa when the welding temperature is 650 °C and the holding time is 30 min. Under this process, the performance of the joint significantly improved under the dual effects of mechanical bonding and metallurgical bonding. This study provides a new idea for the connection of metal and ceramic and has reference value for the selection of the brazing process.
PubDate: Wed, 17 Jul 2024 00:00:00 GMT
DOI: 10.2351/7.0001406
Issue No: Vol. 36, No. 3 (2024)
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- Spatial-temporal characteristics analysis of laser-induced shockwave
pressure by reverse optimization with multi-island genetic algorithm-
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First page: 032019
Abstract: Laser-induced shock wave (LSW) represents a significant phenomenon arising from the interaction between laser radiation and matter. In this study, we establish a finite element and optimization model constrained by a physical framework. Utilizing multichannel photon Doppler velocimeter experimental data as the target for matching, we directly acquire the spatiotemporal pressure characteristics of LSW through the multi-island genetic algorithm. The optimized outcomes show deviations from experimental results within 10%. Research reveals that the spatial uniformity of pressure deteriorates with increasing power density, accompanied by a gradual reduction in the proportion of peak pressure. Temporally, aside from the pressure caused by plasma, there are some small pressure peaks. When the laser's full width half maximum reaching 100 or 200 ns, the pressure decays prematurely. The duration of pressure does not extend to two to three times the duration of the laser pulse.
PubDate: Fri, 19 Jul 2024 00:00:00 GMT
DOI: 10.2351/7.0001403
Issue No: Vol. 36, No. 3 (2024)
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- Microstructure and properties of SLMed Ta-10W and rolled Ta-10W fiber
laser welded joint-
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First page: 032020
Abstract: This study focused on the mechanical properties and microstructure of fiber laser-welded joints of Ta-10W alloy manufactured by selective laser melting (SLM) and rolled. In the SLMed base material side of the weld, columnar grains were formed along the weld, extending up to half of the weld width. The base material’s anisotropy influenced the subgrain morphology, and grain orientation changed after welding. When the building direction of the SLMed Ta-10W was perpendicular to the welding direction, slender columnar subgrains were prone to forming in the SLM side weld. In contrast, when the building direction was parallel to the welding direction, equiaxed subgrains tended to form in the weld. In the rolling base material side weld, mainly equiaxed grains were formed, with subgrain morphology and orientation randomly distributed. In the weld center, fine-grain zones of 10–20 μm, comprising fine grains of 2–5 μm diameter, were observed in all welds under study. Room-temperature tensile strengths of both welds were approximately 620 MPa, falling between the strengths of the two base materials. Their fracture surfaces displayed a mixed mode of cleavage and intergranular fracture. High-temperature strengths of rolled-SLMed joints varied with SLM directions X and Z, reaching 124.94 and 107.87 MPa, respectively, and exhibiting similar fracture characteristics dominated by intergranular fracture.
PubDate: Mon, 22 Jul 2024 00:00:00 GMT
DOI: 10.2351/7.0001410
Issue No: Vol. 36, No. 3 (2024)
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- Effects of surface roughness on the microstructure and mechanical
properties of dissimilar sapphire/Invar36 alloy joints made by ultrashort
pulsed laser micro-welding-
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First page: 032021
Abstract: The ultrashort pulsed (USP) laser microwelding of sapphire/lnvar36 alloy controlled by the surface roughness of metal was investigated for the first time. The surface roughness (Sa) of Invar alloys gradually decreased from 0.944 to 0.029 μm from the prime surface to grounded and polished surface. However, the joint shear strength first increased and then decreased with the lowered Sa, the maximum shear strength reached 107.87 MPa at the Sa ∼ 0.131 μm. Compared to other surfaces with low Sa, the relatively high surface roughness enhanced the interfacial thermal deposition both spatially and temporally which in turn promoted the diffusion of interface elements and the formation of jagged mechanical interlocking structures. Therefore, the appropriate rough metal surface was beneficial for the enhancement of sapphire/metal dissimilar joints. This report is of great significance in simplifying the surface preparation process in the USP laser microwelding of transparent hard and brittle materials with metals, therefore promoting this technique from lab to industry.
PubDate: Fri, 26 Jul 2024 00:00:00 GMT
DOI: 10.2351/7.0001513
Issue No: Vol. 36, No. 3 (2024)
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- Effects of Cr and Mo content on the microstructure and properties of
Fe-based amorphous composite coatings by laser cladding-
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First page: 032022
Abstract: In this study, we successfully produced Fe-based amorphous composite coatings on the surface of 45 steel using laser cladding technology, and the impact of the relative content of Cr and Mo elements on the microstructure, hardness, and wear resistance of composite coatings has been investigated. The results show that the microstructure of the coating changes from dendrite to amorphous nanocrystalline when the content of Cr and Mo is 20 and 15 wt. %, respectively. However, when the Mo element continues to be added, elemental segregation will be caused, resulting in a large number of brittle Fe–Cr–Mo intermetallic compounds and MoSi2 ceramic phases in the coating. Therefore, the appropriate element ratio can not only increase the amorphous phase content in the coating but also prevent elemental segregation. Among the three types of amorphous composite coatings studied, the Fe45Cr20Mo15B10Si10 (wt. %) composite coating exhibited the most favorable performance, primarily due to its highest amorphous content (43.33%). Through the interaction of the amorphous phase, α-Fe, Fe–Cr solid solution, and a small proportion of intermetallic compounds, this coating achieved a hardness of 1282.8 HV0.2, approximately five times that of the 45 steel substrate, and demonstrated superior wear resistance.
PubDate: Tue, 30 Jul 2024 00:00:00 GMT
DOI: 10.2351/7.0001392
Issue No: Vol. 36, No. 3 (2024)
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- Hybrid use of a robotic welding system in remote laser separation of
thin-sheet Al casings for the recycling of battery packs-
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First page: 032023
Abstract: Robotic systems equipped with high-power laser sources are often employed for the production of battery packs for the electric mobility sector. Considering the strive toward a circular manufacturing economy, there is great interest in the possibility of reconfiguring such equipment for dismantling operations. The present study explores the hybrid use of a robotized fiber laser welding system, adapting its scope from joining of battery casings toward the separation of the same thin Al sheets, enabling the recycling of the internal cells of the battery pack. Process feasibility is assessed by tailoring the beam size as well as exploiting dynamic beam oscillation to perform the separation process. Dynamic beam oscillation allows us to obtain a smaller kerf width and greater process stability with respect to linear trajectories with larger beam sizes. The damage to underlying cells of the separation region was also assessed on different materials (Al, Ni-plated steel, and Cu). Greater surface modifications and higher peak temperatures (in excess of 800 °C) were recorded when employing dynamic beam oscillation with respect to linear trajectories. This research demonstrates a pathway for reutilization of the existing technological systems for a circular and sustainable production chain in the e-mobility sector.
PubDate: Fri, 02 Aug 2024 00:00:00 GMT
DOI: 10.2351/7.0001359
Issue No: Vol. 36, No. 3 (2024)
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- Surface tension derivation from laser-generated keyholes
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First page: 032024
Abstract: Surface tension is an essential material property that defines many aspects of thermal processes involving liquids. Metal materials have high melting temperatures, and surface tension could often be measured around melting temperature and is, therefore, known for many pure materials and simple material systems. However, high-energy input during laser, electron beam, or plasma processes is known to increase the material temperatures far above the melting point. To build theoretical models, simulate processes, and increase process understanding, surface tension values at those high temperatures would be beneficial to know. However, it can be difficult to create stable circumstances and measure surface tension in those conditions. Therefore, it is suggested in this work to indirectly derive surface tension values from the pressure balance inside keyholes created during laser deep penetration processing. A variety of different keyhole shapes were created using dynamic beam shaping by means of coherent beam combining. From the observed keyhole shapes using inline x-ray observations, temperature distributions on the keyhole walls were calculated using ray tracing. The temperature defines the local recoil pressure that counteracts the surface tension pressure, which contains the surface tension value as the only unknown variable. At increasing temperatures above the boiling point, an increasing surface tension was observed.
PubDate: Fri, 02 Aug 2024 00:00:00 GMT
DOI: 10.2351/7.0001525
Issue No: Vol. 36, No. 3 (2024)
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- Experimental study and parameter optimization of laser wire additive
manufacturing of titanium alloy-
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First page: 032025
Abstract: In the single-pass multilayer deposition process of laser wire additive manufacturing, variations in process parameters significantly influence the morphology of the deposited layer. This study experimentally investigates how the main process parameters (laser power, scanning speed, and wire feeding speed) affect the morphology of the deposited layer. It was found that each parameter has distinct effects on the geometrical morphology of deposition. Simultaneously, aiming to enhance the surface topography of the deposited layer and its bonding with the substrate, three optimization objectives are defined. An optimization model is then constructed using experimental data to refine the process parameters. The optimal parameters are determined through experimentation, resulting in significant enhancement of the deposited layer’s topography.
PubDate: Fri, 09 Aug 2024 00:00:00 GMT
DOI: 10.2351/7.0001516
Issue No: Vol. 36, No. 3 (2024)
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- Parametric study of the laser energy absorption in high-power laser beam
welding-
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First page: 032026
Abstract: Laser energy absorption on the keyhole wall is decisive for the thermodynamic behavior and the resultant weld properties in the high-power laser beam welding process. However, its highly transient nature on a microsecond scale makes the quantitative analysis challenging. In this paper, the influence of the relevant welding parameters on laser energy absorption is studied statistically by utilizing multiphysical modeling, in which the three-dimensional transient keyhole dynamics and thermo-fluid flow are calculated. A dynamic mesh adaption technique and a localized level-set-based ray-tracing method are employed to improve the model accuracy further. The results show that the focus position has a remarkable effect on the time-averaged laser absorption, and in contrast, the laser energy distribution regime is only slightly influenced by the welding speed in the studied parameter range (1.5–3.0 m/min). The absorption ratio of the laser energy on the keyhole front wall decreases with increasing welding speed and increases with upward-moving focus positions. The comparison between the calculated results and the experimental measurements ensures the validity of the proposed model.
PubDate: Mon, 12 Aug 2024 00:00:00 GMT
DOI: 10.2351/7.0001537
Issue No: Vol. 36, No. 3 (2024)
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- Rapid detection and discrimination of plant leaves using laser-induced
breakdown spectroscopy-
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First page: 032027
Abstract: The wide diversity of species and the remarkable variation in morphological features that allow plants to adapt to a wide range of terrestrial environments is a fact that highlights the fundamental and crucial role of plants in the field of biodiversity studies. Currently, research on leaf classification is limited and in its early stages. A novel classification system based on laser-induced breakdown spectroscopy (LIBS) technology was proposed in this paper, integrated with machine learning for real-time, in situ detection and analysis of leaves. Four representative leaf samples—Ilex chinensis, Camellia japonica, Cinnamomum camphora, and Osmanthus fragrans—were subjected to spectral analysis and machine learning techniques. Spectral analysis revealed distinct spectral lines corresponding to elements such as Ca, Al, Mg, Na, and Fe, alongside common elements including C, N, and O. Principal component analysis (PCA) was employed to reduce the dimensionality of the spectral data, and the first 13 principal components used in this study captured 98.76% of the total variance. Following this, support vector machine (SVM), backpropagation artificial neural network and convolutional neural network (CNN) algorithms were applied for machine learning on the principal components to develop leaf recognition classification models. Through comparison, the CNN algorithm, boasting a classification accuracy of up to 94.44%, was ultimately selected. The models established by SVM and back propagation artificial neural network achieved accuracy of only 83.33% and 90.00%, respectively. The results suggest that integrating LIBS with machine learning is an effective and precise approach for leaf classification, offering promising applications in biodiversity research.
PubDate: Tue, 13 Aug 2024 00:00:00 GMT
DOI: 10.2351/7.0001536
Issue No: Vol. 36, No. 3 (2024)
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- Laser wafer dicing process optimization using the Taguchi approach
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First page: 032028
Abstract: This study uses an infrared cutting laser system to dice GaAs wafers. The Taguchi method determines the laser wafer dicing parameters [laser power (W), depth of focus (μm), and platform speed (m/s)] in relation to the dicing yield and single-grain compressive strength. An orthogonal array (L9 33), a signal-to-noise ratio, and an analysis of variance are employed to study the effects of these parameters. The result shows that the laser wafer dicing yield ranges from 85.53% to 95.20%, with laser power accounting for 86.08% of the total variation, making it the most significant factor. Additionally, the wafer dicing yield is positively correlated with grain compressive strength. Grain defects and corner chipping produced during the cutting process will reduce the compressive strength of the grains. Under the optimized laser wafer cutting conditions, the dicing yield and grain compressive strength reached 95.87% and 331.93 N/mm2, respectively.
PubDate: Tue, 13 Aug 2024 00:00:00 GMT
DOI: 10.2351/7.0001409
Issue No: Vol. 36, No. 3 (2024)
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- Adaptive hybrid control for the formed morphology in powder-based laser
metal deposition-
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First page: 032029
Abstract: The application of powder-based laser metal deposition in the field of industrial production has been limited for the formed geometrical morphology and mechanical performance of additive manufacturing parts. Process variable monitoring and feedback control of the deposition process is an effective method to improve the dimensional accuracy of the manufactured part. In this study, distinguished from the earlier research on processing technology of objects with a small size and a simple structure, an adaptive hybrid control method was proposed for the parts that were relatively complex in structures and required a long period of multilayer deposition. First, laser power was dynamically adjusted in real time based on the adaptive fuzzy proportional integral control algorithm to maintain the stability of each deposited layer through the monitoring of the molten pool temperature. Then, the deposited height was collected in stages and a compensation control method for the adjustment of powder feeding rate was developed. Finally, the hybrid control method was verified through the manufacture of a typical thin wall U-shaped part made of Ti6Al4V. Results show that compared to the open-loop process, deposited height deviation and the wall thickness deviation of the U-shaped part are reduced by 94.36% and 98.95%, respectively, and the surface quality is effectively improved with the value of the surface roughness (root mean square height, Sq) reduced by 70.68%. In addition, a maximum overlap volume ratio of 91.77% between the deposited model and the designed geometrical model was obtained.
PubDate: Thu, 15 Aug 2024 00:00:00 GMT
DOI: 10.2351/7.0001519
Issue No: Vol. 36, No. 3 (2024)
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- Effect of laser surface melting on microstructure and properties of
Mg-1Mn-2Zn alloy-
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First page: 032030
Abstract: With its excellent biocompatibility and degradability, magnesium alloy has now been widely used as a promising medical metal material in clinical medical research, but its application in this field is greatly limited by shortcomings such as too fast and uncontrollable corrosion rate and poor wear resistance of magnesium alloys. In this paper, the self-prepared Mg-1Mn-2Zn alloy was subjected to laser surface melting (LSM) under different process parameters after T6 aging treatment to study the organizational properties of Mg-1Mn-2Zn alloy before and after laser melting treatment and under different scanning speeds. The results show that after LSM, a melting layer is formed on the surface of Mg-1Mn-2Zn alloy, and the grain size of the melting layer is significantly refined, with an average size of 5 μm, and the hardness of the melting layer was improved. The second phase content was reduced, and the wear resistance and corrosion resistance of the melting layer were improved to different degrees. Relevant research can provide theoretical basis for the promotion of medical magnesium alloys.
PubDate: Wed, 21 Aug 2024 00:00:00 GMT
DOI: 10.2351/7.0001413
Issue No: Vol. 36, No. 3 (2024)
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- Identifying the direction of weld path deviations in laser deep
penetration welding of hidden T-joints by means of OCT-
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First page: 032031
Abstract: In laser beam welding of hidden T-joints, the web sheet is completely covered by the face sheet, thus impeding the determination of the relative position between the laser beam and the web sheet. This circumstance usually raises high demands on the clamping accuracy, as an in-process correction of the beam path by means of optical reference measurements is difficult. Previous research has shown that optical coherence tomography is capable of distinguishing between alignment or misalignment between the beam position and the web sheet. While this distinction has already been employed for controlling the weld path, it is not yet possible to determine from the measurement data the information in which direction the laser deviates from the web sheet, resulting in a random initial guess for the beam path correction. In this research, the asymmetry of the process zone when deviating from the web sheet position is exploited to derive information about the direction in which the weld path deviation occurs. For this purpose, the optical coherence tomography (OCT) probe beam is shifted laterally to the laser beam to capture asymmetric keyhole features that are specific for the respective direction of the weld path deviation. The OCT signals are evaluated by means of analytical approaches as well as neural networks. It is shown that the direction of the weld path deviation can often be determined from the OCT measurement data, thus allowing for a loopless setting of initial beam path correction.
PubDate: Thu, 22 Aug 2024 00:00:00 GMT
DOI: 10.2351/7.0001566
Issue No: Vol. 36, No. 3 (2024)
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- Publisher’s Note: “Material incorporation in powder sheet additive
manufacturing toward lightweight designs for future mobility” [J. Laser
Appl. 36, 022026 (2024)]-
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First page: 039901
Abstract: This article was originally published online on 16 May 2024 with data from the second row, third and fourth columns of Table I placed incorrectly in the third row. Table I appears correctly below.
PubDate: Thu, 13 Jun 2024 00:00:00 GMT
DOI: 10.2351/7.0001524
Issue No: Vol. 36, No. 3 (2024)
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