Despite the maturity of laser-based powder bed fusion of metals (PBF-LB/M), some barriers prevent the manufacturing process from fully being established in the industry. One drawback is spatter formation, which is disadvantageous to PBF-LB/M for three main reasons. First, adhering spatter can initiate coater collision, resulting in process failure. Second, large adhering spatter may cause lack-of-fusion defects as they require more energy to remelt sufficiently compared to unprocessed powder. Furthermore, big nonadhering spatter cannot be recycled as powder. The recycling of small spatter particles potentially results in degraded material properties. Ring-shaped beam profiles have been established for deep penetration welding to reduce spatter formation. Investigations on ring-shaped beam profiles in PBF-LB/M focus on improving productivity and process robustness. Qualitative spatter reduction in PBF-LB/M using ring-shaped beam profiles has also been reported. This publication quantitatively examines the influence of ring-shaped beam profiles on spatter formation in PBF-LB/M. Image processing algorithms of on-axis high-speed images are utilized for spatter detection and tracking. A self-developed spatter segmentation is used to determine the spatter size. A Laplacian of Gaussian filter is combined with a Kalman tracker to count and track the spatter. The results show that spatter formation is highly influenced by the beam profile and the chosen process parameters. Considering the melt track width, ring-shaped beam profiles could reduce the number of spatter per fused area. High numbers of spatter are generated when parameter sets result in balling. Moreover, spatter velocity is primarily dependent on the introduced dimensionless enthalpy.
{"title":"Influence of ring-shaped beam profiles on spatter characteristics in laser-based powder bed fusion of metals","authors":"Jonas Grünewald, Jan Reimann, Katrin Wudy","doi":"10.2351/7.0001153","DOIUrl":"https://doi.org/10.2351/7.0001153","url":null,"abstract":"Despite the maturity of laser-based powder bed fusion of metals (PBF-LB/M), some barriers prevent the manufacturing process from fully being established in the industry. One drawback is spatter formation, which is disadvantageous to PBF-LB/M for three main reasons. First, adhering spatter can initiate coater collision, resulting in process failure. Second, large adhering spatter may cause lack-of-fusion defects as they require more energy to remelt sufficiently compared to unprocessed powder. Furthermore, big nonadhering spatter cannot be recycled as powder. The recycling of small spatter particles potentially results in degraded material properties. Ring-shaped beam profiles have been established for deep penetration welding to reduce spatter formation. Investigations on ring-shaped beam profiles in PBF-LB/M focus on improving productivity and process robustness. Qualitative spatter reduction in PBF-LB/M using ring-shaped beam profiles has also been reported. This publication quantitatively examines the influence of ring-shaped beam profiles on spatter formation in PBF-LB/M. Image processing algorithms of on-axis high-speed images are utilized for spatter detection and tracking. A self-developed spatter segmentation is used to determine the spatter size. A Laplacian of Gaussian filter is combined with a Kalman tracker to count and track the spatter. The results show that spatter formation is highly influenced by the beam profile and the chosen process parameters. Considering the melt track width, ring-shaped beam profiles could reduce the number of spatter per fused area. High numbers of spatter are generated when parameter sets result in balling. Moreover, spatter velocity is primarily dependent on the introduced dimensionless enthalpy.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135740160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Enhancing the durability of molds, jigs, and tools is crucial for the industry, and one approach to achieve this is by forming a metallic layer with high hardness on their surfaces. Metallic layers with high hardness can be formed through laser metal deposition (LMD), which is one of the additive manufacturing processes, using cemented carbide powder. However, crack initiation typically occurs inside cemented carbide layers formed by the LMD. Therefore, achieving a cladding process for cemented carbide layers without cracks is desired for practical applications. In this study, the effects of tungsten carbide (WC) ratios in WC-Co cemented carbide granulated powder on formed bead size and crack initiation during the LMD processing were investigated. The number of cracks generated during the LMD processing was evaluated using an acoustic emission (AE) technique. The number of burst-type AE signals generated was counted as the number of cracks. Seven types of WC-Co cemented carbide granulated powders with WC ratios ranging from 30.5 to 92 mass% were prepared. Beads were formed using each powder through the LMD, with AE signals being measured. In the case of a WC ratio of 42.9 mass% or less, no crack was observed. On the other hand, cracks were observed when the WC ratio was 53.9 mass% or greater, and the number of cracks increased with an increase in the WC ratio.
{"title":"Effects of WC ratios on bead size and crack initiation in forming WC-Co cemented carbides by the laser metal deposition","authors":"Yorihiro Yamashita, Mitsuki Nakamura, Takahiro Kunimine, Yuji Sato, Yoshinori Funada, Masahiro Tsukamoto","doi":"10.2351/7.0001101","DOIUrl":"https://doi.org/10.2351/7.0001101","url":null,"abstract":"Enhancing the durability of molds, jigs, and tools is crucial for the industry, and one approach to achieve this is by forming a metallic layer with high hardness on their surfaces. Metallic layers with high hardness can be formed through laser metal deposition (LMD), which is one of the additive manufacturing processes, using cemented carbide powder. However, crack initiation typically occurs inside cemented carbide layers formed by the LMD. Therefore, achieving a cladding process for cemented carbide layers without cracks is desired for practical applications. In this study, the effects of tungsten carbide (WC) ratios in WC-Co cemented carbide granulated powder on formed bead size and crack initiation during the LMD processing were investigated. The number of cracks generated during the LMD processing was evaluated using an acoustic emission (AE) technique. The number of burst-type AE signals generated was counted as the number of cracks. Seven types of WC-Co cemented carbide granulated powders with WC ratios ranging from 30.5 to 92 mass% were prepared. Beads were formed using each powder through the LMD, with AE signals being measured. In the case of a WC ratio of 42.9 mass% or less, no crack was observed. On the other hand, cracks were observed when the WC ratio was 53.9 mass% or greater, and the number of cracks increased with an increase in the WC ratio.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":"361 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135740678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chunliang Yang, Fan Yang, Xiangmeng Meng, Stephen Nugraha Putra, Marcel Bachmann, Michael Rethmeier
Through experimental observation and auxiliary numerical simulation, this investigation studies the different types of grain refinement of 5754 aluminum alloy laser beam welding by applying a transverse oscillating magnetic field. Scanning electron microscope results have proved that the application of a magnetic field can reduce the average crystal branch width and increase its number. The interaction between the induced eddy current generated by the Seebeck effect and the applied external magnetic field produces a Lorentz force, which is important for the increase in the number of crystal branches. Based on the theory of dendrite fragmentation and the magnetic field-induced branches increment, the grain size reduction caused by the magnetic field is studied. Furthermore, the effects of the magnetic field are analyzed by combining a phase field method model and simulations of nucleation and grain growth. The grain distribution and average grain size after welding verify the reliability of the model. In addition, the introduction of a magnetic field can increase the number of periodic three-dimensional solidification patterns. In the intersection of two periods of solidification patterns, the metal can be re-melted and then re-solidified, which prevents the grains, that have been solidified and formed previously, from further growth and generates some small cellular grains in the new fusion line. The magnetic field increases the building frequency of these solidification structures and thus promotes this kind of grain refinement.
{"title":"Experimental and numerical study on grain refinement in electromagnetic assisted laser beam welding of 5754 Al alloy","authors":"Chunliang Yang, Fan Yang, Xiangmeng Meng, Stephen Nugraha Putra, Marcel Bachmann, Michael Rethmeier","doi":"10.2351/7.0001085","DOIUrl":"https://doi.org/10.2351/7.0001085","url":null,"abstract":"Through experimental observation and auxiliary numerical simulation, this investigation studies the different types of grain refinement of 5754 aluminum alloy laser beam welding by applying a transverse oscillating magnetic field. Scanning electron microscope results have proved that the application of a magnetic field can reduce the average crystal branch width and increase its number. The interaction between the induced eddy current generated by the Seebeck effect and the applied external magnetic field produces a Lorentz force, which is important for the increase in the number of crystal branches. Based on the theory of dendrite fragmentation and the magnetic field-induced branches increment, the grain size reduction caused by the magnetic field is studied. Furthermore, the effects of the magnetic field are analyzed by combining a phase field method model and simulations of nucleation and grain growth. The grain distribution and average grain size after welding verify the reliability of the model. In addition, the introduction of a magnetic field can increase the number of periodic three-dimensional solidification patterns. In the intersection of two periods of solidification patterns, the metal can be re-melted and then re-solidified, which prevents the grains, that have been solidified and formed previously, from further growth and generates some small cellular grains in the new fusion line. The magnetic field increases the building frequency of these solidification structures and thus promotes this kind of grain refinement.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135979318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Andreas Maier, Manuel Rühr, Marcel Stephan, Sebastian Frankl, Stephan Roth, Michael Schmidt
Stainless steels are established in various fields with challenging environments, e.g., offshore, petrochemical, and automotive industries. The combination of high-performance properties and high-value added applications makes stainless steels attractive for additive manufacturing (AM). In powder-based AM processes such as laser-directed energy deposition (DED-LB/M), typically prealloyed powders are used for part generation. By an innovative approach called in situ alloying, the chemical composition of prealloyed powder can be adjusted by mixing it with an additional powder material. This allows the material properties to be flexibly and efficiently tailored for specific applications. In this work, a standard duplex stainless steel (DSS) is modified for the first time with elemental powders in order to systematically adjust the resulting phase formation, mechanical properties, and corrosion resistance. For this, powder mixtures were generated consisting of prealloyed DSS 1.4462 and additions of pure chromium (1.0–7.0 wt. %) or nickel (1.0–5.0 wt. %) powder. Processing them by means of DED-LB/M resulted in specimens (rel. density > 99.7%) with ferrite–austenite phase ratios ranging from almost 10%:90% to 90%:10%. Increasing the chromium content successively increased the ferrite percentage, resulting in higher material hardness, higher strength, and resistance against pitting corrosion but poor ductility and toughness compared to unmodified DSS. In contrast, an increased nickel content resulted in an increased austenite formation with lower hardness and strength but increased ductility. This strategy was shown to add flexibility to powder-based AM processes by enabling an on-demand material design for stainless steels.
{"title":"Tailoring material properties of duplex stainless steel by DED-LB/M and <i>in situ</i> alloying with elemental powders","authors":"Andreas Maier, Manuel Rühr, Marcel Stephan, Sebastian Frankl, Stephan Roth, Michael Schmidt","doi":"10.2351/7.0001119","DOIUrl":"https://doi.org/10.2351/7.0001119","url":null,"abstract":"Stainless steels are established in various fields with challenging environments, e.g., offshore, petrochemical, and automotive industries. The combination of high-performance properties and high-value added applications makes stainless steels attractive for additive manufacturing (AM). In powder-based AM processes such as laser-directed energy deposition (DED-LB/M), typically prealloyed powders are used for part generation. By an innovative approach called in situ alloying, the chemical composition of prealloyed powder can be adjusted by mixing it with an additional powder material. This allows the material properties to be flexibly and efficiently tailored for specific applications. In this work, a standard duplex stainless steel (DSS) is modified for the first time with elemental powders in order to systematically adjust the resulting phase formation, mechanical properties, and corrosion resistance. For this, powder mixtures were generated consisting of prealloyed DSS 1.4462 and additions of pure chromium (1.0–7.0 wt. %) or nickel (1.0–5.0 wt. %) powder. Processing them by means of DED-LB/M resulted in specimens (rel. density &gt; 99.7%) with ferrite–austenite phase ratios ranging from almost 10%:90% to 90%:10%. Increasing the chromium content successively increased the ferrite percentage, resulting in higher material hardness, higher strength, and resistance against pitting corrosion but poor ductility and toughness compared to unmodified DSS. In contrast, an increased nickel content resulted in an increased austenite formation with lower hardness and strength but increased ductility. This strategy was shown to add flexibility to powder-based AM processes by enabling an on-demand material design for stainless steels.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":"2022 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135981449","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A Zhanwen, Guisheng Zou, Wenqiang Li, Yue You, Bin Feng, Zimao Sheng, Chengjie Du, Yu Xiao, Jinpeng Huo, Lei Liu
An efficient quality evaluation method is crucial for the applications of high-quality microhole arrays drilled with ultrafast lasers. The vision-based feature extraction was used as a data acquisition method to evaluate the drilling quality in terms of the geometric quality of the hole shape. However, the morphological features such as the recast layer, microcracks, and debris on the surface are difficult to consider in the quality evaluation since simultaneous recognition of multiple features remains challenging. Herein, we successfully recognized and extracted multiple features by deep learning, thus achieving the quality evaluation of microhole arrays in terms of both geometrical and surface qualities. Microhole arrays of various sizes and surface quality are fabricated on copper, stainless steel, titanium, and glass using different processing parameters. Then, the images of the microhole arrays are prepared as the dataset to train the deep learning network by labeling the typical features of microholes. The well-trained deep learning network has efficient and powerful recognition ability. Typical features such as the hole profile, recast layer, microcracks, and debris can be recognized and extracted simultaneously; thereby the geometric and surface quality of the microhole are obtained. We also demonstrate the implementation of the method with a fast quality evaluation of an array of 2300 microholes based on a statistical approach. The methods presented here extend the quality evaluation of microhole arrays by considering both geometric and surface qualities and can also be applied to quality monitoring in other ultrafast laser micromachining.
{"title":"Deep learning driven multifeature extraction for quality evaluation of ultrafast laser drilled microhole arrays","authors":"A Zhanwen, Guisheng Zou, Wenqiang Li, Yue You, Bin Feng, Zimao Sheng, Chengjie Du, Yu Xiao, Jinpeng Huo, Lei Liu","doi":"10.2351/7.0001162","DOIUrl":"https://doi.org/10.2351/7.0001162","url":null,"abstract":"An efficient quality evaluation method is crucial for the applications of high-quality microhole arrays drilled with ultrafast lasers. The vision-based feature extraction was used as a data acquisition method to evaluate the drilling quality in terms of the geometric quality of the hole shape. However, the morphological features such as the recast layer, microcracks, and debris on the surface are difficult to consider in the quality evaluation since simultaneous recognition of multiple features remains challenging. Herein, we successfully recognized and extracted multiple features by deep learning, thus achieving the quality evaluation of microhole arrays in terms of both geometrical and surface qualities. Microhole arrays of various sizes and surface quality are fabricated on copper, stainless steel, titanium, and glass using different processing parameters. Then, the images of the microhole arrays are prepared as the dataset to train the deep learning network by labeling the typical features of microholes. The well-trained deep learning network has efficient and powerful recognition ability. Typical features such as the hole profile, recast layer, microcracks, and debris can be recognized and extracted simultaneously; thereby the geometric and surface quality of the microhole are obtained. We also demonstrate the implementation of the method with a fast quality evaluation of an array of 2300 microholes based on a statistical approach. The methods presented here extend the quality evaluation of microhole arrays by considering both geometric and surface qualities and can also be applied to quality monitoring in other ultrafast laser micromachining.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135982322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Bachmann, A. Artinov, Xiangmeng Meng, Stephen Nugraha Putra, M. Rethmeier
The amount of absorbed energy in the keyhole as well as its spatial and temporal distribution is essential to model the laser beam welding process. The recoil pressure, which develops because of the evaporation process induced by the absorbed laser energy at the keyhole wall, is a key determining factor for the macroscopic flow of the molten metal in the weld pool during high-power laser beam welding. Consequently, a realistic implementation of the effect of laser radiation on the weld metal is crucial to obtain reliable and accurate simulation results. In this paper, we discuss manyfold different improvements on the laser-material interaction, namely, the ray tracing method, in the numerical simulation of the laser beam welding process. The first improvement relates to locating the exact reflection points in the ray tracing method using a so-called cosine condition in the determination algorithm for the intersection of reflected rays and the keyhole surface. A second correction refers to the numerical treatment of the Gaussian distribution of the laser beam, whose beam width is defined by a decay of the laser intensity by a factor of 1/e2, thus ignoring around 14% of the total laser beam energy. In the third step, the changes in the laser radiation distribution in the vertical direction were adapted by using different approximations for the converging and the diverging regions of the laser beam, thus mimicking the beam caustic. Finally, a virtual mesh refinement was adopted in the ray tracing routine. The obtained numerical results were validated with experimental measurements.
{"title":"Challenges in dynamic heat source modeling in high-power laser beam welding","authors":"M. Bachmann, A. Artinov, Xiangmeng Meng, Stephen Nugraha Putra, M. Rethmeier","doi":"10.2351/7.0001079","DOIUrl":"https://doi.org/10.2351/7.0001079","url":null,"abstract":"The amount of absorbed energy in the keyhole as well as its spatial and temporal distribution is essential to model the laser beam welding process. The recoil pressure, which develops because of the evaporation process induced by the absorbed laser energy at the keyhole wall, is a key determining factor for the macroscopic flow of the molten metal in the weld pool during high-power laser beam welding. Consequently, a realistic implementation of the effect of laser radiation on the weld metal is crucial to obtain reliable and accurate simulation results. In this paper, we discuss manyfold different improvements on the laser-material interaction, namely, the ray tracing method, in the numerical simulation of the laser beam welding process. The first improvement relates to locating the exact reflection points in the ray tracing method using a so-called cosine condition in the determination algorithm for the intersection of reflected rays and the keyhole surface. A second correction refers to the numerical treatment of the Gaussian distribution of the laser beam, whose beam width is defined by a decay of the laser intensity by a factor of 1/e2, thus ignoring around 14% of the total laser beam energy. In the third step, the changes in the laser radiation distribution in the vertical direction were adapted by using different approximations for the converging and the diverging regions of the laser beam, thus mimicking the beam caustic. Finally, a virtual mesh refinement was adopted in the ray tracing routine. The obtained numerical results were validated with experimental measurements.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43845382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to achieve sustainable development goals, decarbonization and low-carbonization are required. Electric and hybrid vehicles are indispensable for the conservation of natural environment, and the lightweight construction and the effective transfer of electricity become important. Thus, copper and aluminum have been increasingly recognized as important materials because of their excellent materials’ properties. However, in the welding of these materials, it is difficult to obtain strong joints because there are problems in the brittle intermetallic compounds and the welding defects due to different melting points between copper and aluminum. Especially in the joining of copper and aluminum by copper side irradiation, aluminum-rich intermetallic compounds (IMCs) of brittle state result in the decrease of mechanical strength. Therefore, mild heat input from copper to aluminum would be necessary to reduce the brittle IMC. Angled irradiation might result in the mild energy input to aluminum because it can be expected that aluminum would be heated by the reflected light inside the keyhole generated in copper according to its high light reflection. In addition, stable welding can be expected by the superposed irradiation of blue and near-infrared lasers because of high light absorption rate of blue laser to copper. The angled and the superposed irradiation could achieve a stable welding state, and the generation of aluminum-rich IMC becomes smaller. Angled irradiation of a near-infrared laser showed equivalent joining strength to the superposed irradiation of two wavelengths, and the combination of angled and superposed irradiation achieved a remarkable increase of joining strength in a cross tensile test by 80%.
{"title":"Fundamental study on high-quality welding of copper and aluminum by angled and superposed irradiation of blue and near-infrared lasers","authors":"Yuki Yamada, Yasuhiro Okamoto, Akira Okada, N. Nishi, Takeshi Yamamura, Katsutoshi Nagasaki, Kazunobu Mameno","doi":"10.2351/7.0001096","DOIUrl":"https://doi.org/10.2351/7.0001096","url":null,"abstract":"In order to achieve sustainable development goals, decarbonization and low-carbonization are required. Electric and hybrid vehicles are indispensable for the conservation of natural environment, and the lightweight construction and the effective transfer of electricity become important. Thus, copper and aluminum have been increasingly recognized as important materials because of their excellent materials’ properties. However, in the welding of these materials, it is difficult to obtain strong joints because there are problems in the brittle intermetallic compounds and the welding defects due to different melting points between copper and aluminum. Especially in the joining of copper and aluminum by copper side irradiation, aluminum-rich intermetallic compounds (IMCs) of brittle state result in the decrease of mechanical strength. Therefore, mild heat input from copper to aluminum would be necessary to reduce the brittle IMC. Angled irradiation might result in the mild energy input to aluminum because it can be expected that aluminum would be heated by the reflected light inside the keyhole generated in copper according to its high light reflection. In addition, stable welding can be expected by the superposed irradiation of blue and near-infrared lasers because of high light absorption rate of blue laser to copper. The angled and the superposed irradiation could achieve a stable welding state, and the generation of aluminum-rich IMC becomes smaller. Angled irradiation of a near-infrared laser showed equivalent joining strength to the superposed irradiation of two wavelengths, and the combination of angled and superposed irradiation achieved a remarkable increase of joining strength in a cross tensile test by 80%.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43601209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Daniel Maiwald, S. Nothdurft, J. Hermsdorf, S. Kaierle
Brass represents a large part in the production of components within the copper alloy group. Laser beam welding of this alloy offers great potential for many applications in terms of achievable seam quality and productivity. However, there is a very high tendency of the process for irregular seam surfaces and formation of pores as well as spatters. These are due, among other things, to instabilities of the keyhole, which is favored by the evaporation of the alloy component zinc. Furthermore, near-infrared laser beam wavelength can couple poorly into the material due to the low absorption level of brass, whereas absorption jumps during the melt transition. In recent years, high-brilliance near-infrared laser beam sources with adjustable beam profiles have been developed, to contribute to the stabilization of the keyhole. The presented experimental process investigations are on deep penetration welding of different brass alloys (CuZn37 and CuZn39Pb3). A laser beam source with a power of 6000 W and a combined core and ring beam was used for this purpose. It was found that the process parameters, such as energy per unit length, spot size, and process gas supply, have a significant impact on the resulting weld seam. These parameters were systematically varied. The produced seams were analyzed and evaluated using various methods, including micrograph analysis, energy dispersive x-ray spectroscopy, 3D-computed tomography, and 3D-topography imaging. The results were then correlated with the process parameters. Process parameters that produce high-quality bead-on-plate and butt welds for a sheet thicknesses of 2 mm were determined.
{"title":"Laser beam welding of brass with combined core and ring beam","authors":"Daniel Maiwald, S. Nothdurft, J. Hermsdorf, S. Kaierle","doi":"10.2351/7.0001164","DOIUrl":"https://doi.org/10.2351/7.0001164","url":null,"abstract":"Brass represents a large part in the production of components within the copper alloy group. Laser beam welding of this alloy offers great potential for many applications in terms of achievable seam quality and productivity. However, there is a very high tendency of the process for irregular seam surfaces and formation of pores as well as spatters. These are due, among other things, to instabilities of the keyhole, which is favored by the evaporation of the alloy component zinc. Furthermore, near-infrared laser beam wavelength can couple poorly into the material due to the low absorption level of brass, whereas absorption jumps during the melt transition. In recent years, high-brilliance near-infrared laser beam sources with adjustable beam profiles have been developed, to contribute to the stabilization of the keyhole. The presented experimental process investigations are on deep penetration welding of different brass alloys (CuZn37 and CuZn39Pb3). A laser beam source with a power of 6000 W and a combined core and ring beam was used for this purpose. It was found that the process parameters, such as energy per unit length, spot size, and process gas supply, have a significant impact on the resulting weld seam. These parameters were systematically varied. The produced seams were analyzed and evaluated using various methods, including micrograph analysis, energy dispersive x-ray spectroscopy, 3D-computed tomography, and 3D-topography imaging. The results were then correlated with the process parameters. Process parameters that produce high-quality bead-on-plate and butt welds for a sheet thicknesses of 2 mm were determined.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43778594","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Melika Esmaeili, Atoosa Sadat Arabanian, Somayeh Najafi, R. Massudi
A two-temperature model (TTM) for the electron-phonon thermal equilibrium is used to determine the heat distribution and laser fluence threshold for melting a thin metal film coated on a glass substrate and irradiated by an ultrashort laser pulse. This study proposes a novel model based on the Navier–Stokes equation to explain the formation of jet-shaped structures in the film's molten region. By solving this equation and obtaining the temporal evolution of the velocity distribution and displacement in the molten region, the Marangoni convection effect can be numerically demonstrated, and the circular motion of the fluid can describe the formation of a jet-shaped structure in the central region of the radiation. The results are compared to those obtained by numerically solving the thermo-elastoplastic equations, and also, to the previously reported experimental results to ensure the accuracy of the microjet height calculated by the Navier–Stokes equation. Good agreement is observed, particularly when the temperature of the irradiated area is significantly over the film's melting temperature. In addition, several calculations are performed for various pulse fluences. In both models, increasing the pulse fluences leads to an increase in the height of microjets.
{"title":"Numerical study of ultrashort laser-induced microjet formation on the metal film based on the Navier–Stokes equation","authors":"Melika Esmaeili, Atoosa Sadat Arabanian, Somayeh Najafi, R. Massudi","doi":"10.2351/7.0001027","DOIUrl":"https://doi.org/10.2351/7.0001027","url":null,"abstract":"A two-temperature model (TTM) for the electron-phonon thermal equilibrium is used to determine the heat distribution and laser fluence threshold for melting a thin metal film coated on a glass substrate and irradiated by an ultrashort laser pulse. This study proposes a novel model based on the Navier–Stokes equation to explain the formation of jet-shaped structures in the film's molten region. By solving this equation and obtaining the temporal evolution of the velocity distribution and displacement in the molten region, the Marangoni convection effect can be numerically demonstrated, and the circular motion of the fluid can describe the formation of a jet-shaped structure in the central region of the radiation. The results are compared to those obtained by numerically solving the thermo-elastoplastic equations, and also, to the previously reported experimental results to ensure the accuracy of the microjet height calculated by the Navier–Stokes equation. Good agreement is observed, particularly when the temperature of the irradiated area is significantly over the film's melting temperature. In addition, several calculations are performed for various pulse fluences. In both models, increasing the pulse fluences leads to an increase in the height of microjets.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46458786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Luisa-Marie Heine, Andreas Heider, Roland Gauch, Mathias Schlett, Marc Hummel, Christoph Spurk, Felix Beckmann, J. Moosmann
In the recent years, laser beam welding has become an established joining process, especially for components in the electrical powertrain (copper applications). However, laser beam welding of copper is generally considered to be difficult, particularly due to its high heat conductivity and due to its low absorptivity using laser sources with a wavelength of 1 μm. The resulting welds show numerous weld defects, such as pores and spatters. Using “blue” lasers with a wavelength of 450 nm promises a smoother welding process with less spatters. Therefore, a blue diode laser with increased absorptivity in copper materials was developed by Laserline and used for welding copper. In this contribution, the results of welding copper using blue lasers with respect to the penetration depth and the resulting weld quality are discussed. In addition, investigations by Bosch at the electron-synchrotron DESY with a blue diode laser enabled us to have a look into the material during welding. Consequently, melt pool dynamics and capillary dynamics were analyzed with respect to the formation of weld defects and will be discussed as well. Furthermore, it is demonstrated that it can be beneficial to use a so-called spot-in-spot beam shaping tool to further improve the melt pool dynamics and, therefore, the resulting weld quality.
{"title":"Blue diode lasers: Evaluation of capillary and melt pool dynamics","authors":"Luisa-Marie Heine, Andreas Heider, Roland Gauch, Mathias Schlett, Marc Hummel, Christoph Spurk, Felix Beckmann, J. Moosmann","doi":"10.2351/7.0001092","DOIUrl":"https://doi.org/10.2351/7.0001092","url":null,"abstract":"In the recent years, laser beam welding has become an established joining process, especially for components in the electrical powertrain (copper applications). However, laser beam welding of copper is generally considered to be difficult, particularly due to its high heat conductivity and due to its low absorptivity using laser sources with a wavelength of 1 μm. The resulting welds show numerous weld defects, such as pores and spatters. Using “blue” lasers with a wavelength of 450 nm promises a smoother welding process with less spatters. Therefore, a blue diode laser with increased absorptivity in copper materials was developed by Laserline and used for welding copper. In this contribution, the results of welding copper using blue lasers with respect to the penetration depth and the resulting weld quality are discussed. In addition, investigations by Bosch at the electron-synchrotron DESY with a blue diode laser enabled us to have a look into the material during welding. Consequently, melt pool dynamics and capillary dynamics were analyzed with respect to the formation of weld defects and will be discussed as well. Furthermore, it is demonstrated that it can be beneficial to use a so-called spot-in-spot beam shaping tool to further improve the melt pool dynamics and, therefore, the resulting weld quality.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46072884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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