Pub Date : 2025-03-24DOI: 10.1016/j.addma.2025.104760
Zhenbang Liu , Mingyang Li , Xiangyu Wang , Teck Neng Wong , Ming Jen Tan
3D concrete printing (3DCP) elements show significant mechanical anisotropy. Printing parameters can affect the mechanical anisotropy of 3DCP elements. However, most studies have focused on the effects of printing parameters on the interlayer bond strength at a macroscale level. The mechanisms of printing parameters on the mechanical anisotropy of 3DCP elements remain unclear. To fill research gaps, computed tomography (CT) scans, computational fluid dynamics (CFD) numerical simulations, and uniaxial compression tests (UCTs) were conducted with the printing parameters of the expansion state of the nozzle flow channel, overflow ratio, stand-off distance, and flow rate involved. The results of CT scans, CFD simulations, and UCTs revealed the mechanism that the printing parameters affect porosity distribution and pore anisotropy by influencing the normalized local pressure at interlayer and fluid velocity gradients, respectively, which further results in the modification of the mechanical anisotropy of 3DCP elements.
{"title":"Investigate mechanisms of different printing parameters on the mechanical anisotropy of 3D concrete printing elements by using computed tomography scan and computational fluid dynamics methods","authors":"Zhenbang Liu , Mingyang Li , Xiangyu Wang , Teck Neng Wong , Ming Jen Tan","doi":"10.1016/j.addma.2025.104760","DOIUrl":"10.1016/j.addma.2025.104760","url":null,"abstract":"<div><div>3D concrete printing (3DCP) elements show significant mechanical anisotropy. Printing parameters can affect the mechanical anisotropy of 3DCP elements. However, most studies have focused on the effects of printing parameters on the interlayer bond strength at a macroscale level. The mechanisms of printing parameters on the mechanical anisotropy of 3DCP elements remain unclear. To fill research gaps, computed tomography (CT) scans, computational fluid dynamics (CFD) numerical simulations, and uniaxial compression tests (UCTs) were conducted with the printing parameters of the expansion state of the nozzle flow channel, overflow ratio, stand-off distance, and flow rate involved. The results of CT scans, CFD simulations, and UCTs revealed the mechanism that the printing parameters affect porosity distribution and pore anisotropy by influencing the normalized local pressure at interlayer and fluid velocity gradients, respectively, which further results in the modification of the mechanical anisotropy of 3DCP elements.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"103 ","pages":"Article 104760"},"PeriodicalIF":10.3,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143734905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-24DOI: 10.1016/j.addma.2025.104755
Jiangyou Long , Yujun Zhou , Jinghao Lin , Bingjun Luo , Zhiheng Wu , Xinhong Su
Laser-induced forward transfer (LIFT) can be used to print micrometer-scale metallic three-dimensional (3D) structures. However, the structures produced by this method exhibit high porosity and poor electrical properties due to the non-vertical ejection and loose stacking of transfer particles. In this study, we replace the conventional copper (Cu) monolayer donor film with a chromium-copper (Cr-Cu) bilayer film. We demonstrate that this bilayer enhances laser absorption and improves glass-metal adhesion through the spontaneous formation of a CrOx interlayer. The improved laser absorption reduces the optimal pulse energy required for transfer, while the interlayer stabilizes the transfer process, promoting more vertical ejection of material. This enhanced directionality leads to denser structures, even when the donor and receiver are placed at a larger distance. The resulting structures exhibit a porosity of 4.8 % and a specific resistance 2.9 times that of bulk copper. Cross-sectional electron microscopy is employed to investigate the microstructure and elucidate the mechanisms behind the reduced resistance. Additionally, we demonstrate the application of this 3D printing method in creating high aspect ratio microstructures and repairing open defects on printed circuit boards (PCBs).
{"title":"Printing dense and low-resistance copper microstructures via highly directional laser-induced forward transfer","authors":"Jiangyou Long , Yujun Zhou , Jinghao Lin , Bingjun Luo , Zhiheng Wu , Xinhong Su","doi":"10.1016/j.addma.2025.104755","DOIUrl":"10.1016/j.addma.2025.104755","url":null,"abstract":"<div><div>Laser-induced forward transfer (LIFT) can be used to print micrometer-scale metallic three-dimensional (3D) structures. However, the structures produced by this method exhibit high porosity and poor electrical properties due to the non-vertical ejection and loose stacking of transfer particles. In this study, we replace the conventional copper (Cu) monolayer donor film with a chromium-copper (Cr-Cu) bilayer film. We demonstrate that this bilayer enhances laser absorption and improves glass-metal adhesion through the spontaneous formation of a CrO<sub><em>x</em></sub> interlayer. The improved laser absorption reduces the optimal pulse energy required for transfer, while the interlayer stabilizes the transfer process, promoting more vertical ejection of material. This enhanced directionality leads to denser structures, even when the donor and receiver are placed at a larger distance. The resulting structures exhibit a porosity of 4.8 % and a specific resistance 2.9 times that of bulk copper. Cross-sectional electron microscopy is employed to investigate the microstructure and elucidate the mechanisms behind the reduced resistance. Additionally, we demonstrate the application of this 3D printing method in creating high aspect ratio microstructures and repairing open defects on printed circuit boards (PCBs).</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"103 ","pages":"Article 104755"},"PeriodicalIF":10.3,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143715396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-21DOI: 10.1016/j.addma.2025.104733
Brodan Richter , Joshua D. Pribe , George R. Weber , Vamsi Subraveti , Caglar Oskay
Powder bed fusion (PBF) additive manufacturing (AM) technology has greatly matured in recent years driven by numerous industrial applications. However, lack-of-fusion (LoF) porosity is a significant challenge during PBF, and LoF pores can form even when processing with optimized deposition parameters. This paper proposes an analytical approach for simulating LoF porosity during PBF AM on the basis of a semi-elliptical model of the melt pool cross-section. Melted area, reference area, and LoF area fraction calculations are developed for the case where only one layer melts the reference area because of a shallow melt pool. In more complex cases where two layers melt a portion of the initial layer, the melted volume, reference volume, and LoF volume fraction calculations are developed using a change of coordinate system and integration. Finally, the model is extended to an arbitrary number of layers by assuming LoF porosity exponentially decays as the number of interacting layers increases. The analytical model predicts LoF porosity for both identical and variable melt pools and enables uncertainty analysis for LoF porosity calculations through the rapid sampling of a large number of experimentally-determined melt pool geometries. The model is used to calculate porosity fraction across the melt pool depth, melt pool width, hatch spacing, and layer thickness processing space. The accuracy of the model is demonstrated through comparisons with experimental data, and the effect of melt pool geometric uncertainty on the PBF process window is demonstrated through experimental comparisons. A new LoF porosity criterion for variable melt pools is proposed that simplifies to a previously defined, widely used LoF porosity criterion in the case of identical melt pools. Overall, the new approach presented provides a straightforward, low computational cost method for calculating LoF porosity that incorporates uncertainty for PBF AM processing.
{"title":"Analytical prediction of lack-of-fusion porosity including uncertainty and variable melt pools for powder bed fusion","authors":"Brodan Richter , Joshua D. Pribe , George R. Weber , Vamsi Subraveti , Caglar Oskay","doi":"10.1016/j.addma.2025.104733","DOIUrl":"10.1016/j.addma.2025.104733","url":null,"abstract":"<div><div>Powder bed fusion (PBF) additive manufacturing (AM) technology has greatly matured in recent years driven by numerous industrial applications. However, lack-of-fusion (LoF) porosity is a significant challenge during PBF, and LoF pores can form even when processing with optimized deposition parameters. This paper proposes an analytical approach for simulating LoF porosity during PBF AM on the basis of a semi-elliptical model of the melt pool cross-section. Melted area, reference area, and LoF area fraction calculations are developed for the case where only one layer melts the reference area because of a shallow melt pool. In more complex cases where two layers melt a portion of the initial layer, the melted volume, reference volume, and LoF volume fraction calculations are developed using a change of coordinate system and integration. Finally, the model is extended to an arbitrary number of layers by assuming LoF porosity exponentially decays as the number of interacting layers increases. The analytical model predicts LoF porosity for both identical and variable melt pools and enables uncertainty analysis for LoF porosity calculations through the rapid sampling of a large number of experimentally-determined melt pool geometries. The model is used to calculate porosity fraction across the melt pool depth, melt pool width, hatch spacing, and layer thickness processing space. The accuracy of the model is demonstrated through comparisons with experimental data, and the effect of melt pool geometric uncertainty on the PBF process window is demonstrated through experimental comparisons. A new LoF porosity criterion for variable melt pools is proposed that simplifies to a previously defined, widely used LoF porosity criterion in the case of identical melt pools. Overall, the new approach presented provides a straightforward, low computational cost method for calculating LoF porosity that incorporates uncertainty for PBF AM processing.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"103 ","pages":"Article 104733"},"PeriodicalIF":10.3,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143739409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-15DOI: 10.1016/j.addma.2025.104740
Taehyub Lee , Chin Siang Ng , Pei-Chen Su
Warp or curl distortion significantly negatively impacts print accuracy and polymer characterization. This issue is exacerbated by the inherent mechanisms of vat photopolymerization (VP) 3d printing. In the VP irradiation step, the amount of the light energy absorbed in the prior layers accumulates, leading to a difference in the degree of curing compared to a newer layer. This causes uneven shrinkage of the individual printing layers, which causes bending deformation. In this study, we corrected the warpage by ensuring uniform light energy absorption across all layers using the modified Beer-Lambert’s law. We investigated the warpage angle of both warped and corrected samples, varying by layer and part thickness. Furthermore, we conducted three-point bending tests of dynamic mechanical analysis (DMA) to verify the consistency of measurements from the corrected samples. The results show significant improvements in warpage across various printing parameters and enhanced consistency in DMA tests. Significantly, this study offers straightforward, robust guidance for setting printing parameters of newly developed resins, ensuring reliable samples to characterize polymers.
{"title":"Warpage correction for vat photopolymerization 3D printing","authors":"Taehyub Lee , Chin Siang Ng , Pei-Chen Su","doi":"10.1016/j.addma.2025.104740","DOIUrl":"10.1016/j.addma.2025.104740","url":null,"abstract":"<div><div>Warp or curl distortion significantly negatively impacts print accuracy and polymer characterization. This issue is exacerbated by the inherent mechanisms of vat photopolymerization (VP) 3d printing. In the VP irradiation step, the amount of the light energy absorbed in the prior layers accumulates, leading to a difference in the degree of curing compared to a newer layer. This causes uneven shrinkage of the individual printing layers, which causes bending deformation. In this study, we corrected the warpage by ensuring uniform light energy absorption across all layers using the modified Beer-Lambert’s law. We investigated the warpage angle of both warped and corrected samples, varying by layer and part thickness. Furthermore, we conducted three-point bending tests of dynamic mechanical analysis (DMA) to verify the consistency of measurements from the corrected samples. The results show significant improvements in warpage across various printing parameters and enhanced consistency in DMA tests. Significantly, this study offers straightforward, robust guidance for setting printing parameters of newly developed resins, ensuring reliable samples to characterize polymers.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"102 ","pages":"Article 104740"},"PeriodicalIF":10.3,"publicationDate":"2025-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143642610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hierarchical structures, such as cellular structures, elemental segregations, and dislocation-network, are often proposed to enhance the mechanical properties of high-entropy alloys (HEAs) fabricated via additive manufacturing (AM). The formation of cellular structures is often attributed to elemental segregation during the solidification process or thermal strain resulting from the AM process. Here, we present a novel cellular structure where phase-separation and dislocation-network coupled in Ti-Zr-Nb-Mo-Ta HEA processed by laser powder bed fusion (L-PBF). Electron microscopy observations and X-ray diffraction (XRD) analyses show that this unique cellular structure consists of Zr-rich and Ta-rich body-center cubic (BCC) phases as the cell-wall and the cell-core, respectively, with their lattice constant difference of about 1 %. Moreover, a higher density of dislocations forming distinct networks is detected within this cellular structure, whose density reached 8 × 1014 m−2. Machine learning analysis reveals that the dislocations preferentially occur on the Zr-rich BCC side, thus accommodating the strains significant around the boundaries between the two BCC phases. With the aid of thermodynamic simulations, we propose a formation mechanism of the present cellular structure, which is governed by the elemental partitioning behavior of Zr and Ta during a solid-state phase separation under rapid cooling. Boundaries with this phase separation are introduced as semi-coherent interfaces with misfit dislocations, introducing a high-density dislocation in the present material. This novel cellular structure can significantly enhance the strength of AM HEAs, providing valuable insights for developing high-performance AM metals through the design of hierarchical microstructures.
{"title":"Phase-separation induced dislocation-network cellular structures in Ti-Zr-Nb-Mo-Ta high-entropy alloy processed by laser powder bed fusion","authors":"Han Chen , Daisuke Egusa , Zehao Li , Taisuke Sasaki , Ryosuke Ozasa , Takuya Ishimoto , Masayuki Okugawa , Yuichiro Koizumi , Takayoshi Nakano , Eiji Abe","doi":"10.1016/j.addma.2025.104737","DOIUrl":"10.1016/j.addma.2025.104737","url":null,"abstract":"<div><div>Hierarchical structures, such as cellular structures, elemental segregations, and dislocation-network, are often proposed to enhance the mechanical properties of high-entropy alloys (HEAs) fabricated via additive manufacturing (AM). The formation of cellular structures is often attributed to elemental segregation during the solidification process or thermal strain resulting from the AM process. Here, we present a novel cellular structure where phase-separation and dislocation-network coupled in Ti-Zr-Nb-Mo-Ta HEA processed by laser powder bed fusion (L-PBF). Electron microscopy observations and X-ray diffraction (XRD) analyses show that this unique cellular structure consists of Zr-rich and Ta-rich body-center cubic (BCC) phases as the cell-wall and the cell-core, respectively, with their lattice constant difference of about 1 %. Moreover, a higher density of dislocations forming distinct networks is detected within this cellular structure, whose density reached 8 × 10<sup>14</sup> m<sup>−2</sup>. Machine learning analysis reveals that the dislocations preferentially occur on the Zr-rich BCC side, thus accommodating the strains significant around the boundaries between the two BCC phases. With the aid of thermodynamic simulations, we propose a formation mechanism of the present cellular structure, which is governed by the elemental partitioning behavior of Zr and Ta during a solid-state phase separation under rapid cooling. Boundaries with this phase separation are introduced as semi-coherent interfaces with misfit dislocations, introducing a high-density dislocation in the present material. This novel cellular structure can significantly enhance the strength of AM HEAs, providing valuable insights for developing high-performance AM metals through the design of hierarchical microstructures.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"102 ","pages":"Article 104737"},"PeriodicalIF":10.3,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143621444","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In additive manufacturing (AM), particularly in laser-based metal AM, process optimization is crucial to the quality of products and the efficiency of production. The identification of optimal process parameters out of a vast parameter space, however, is a daunting task. Despite advances in simulations, the process optimization for specific materials and geometries is developed through a sequential and time-consuming trial-and-error approach and often lacks the versatility to address multiple optimization objectives. Machine learning (ML) provides a powerful tool to accelerate the optimization process, but most current studies focus on simple single-track prints, which hardly translate to manufacturing 3D bulk components for engineering applications. In this study, we develop an Accurate Inverse process optimization framework in laser Directed Energy Deposition (AIDED), based on machine learning models and a genetic algorithm, to aid the process optimization in laser DED. Using AIDED, we demonstrate the following: (i) Accurate prediction of the area of single-track melt pool (R2 score 0.995), the tilt angle of multi-track melt pool (R2 score 0.969), and the cross-sectional geometries of multi-layer melt pool (1.75 % and 12.04 % errors in width and height, respectively) directly from process parameters; (ii) Determination of appropriate hatch spacing and layer thickness for fabricating fully dense (density > 99.9 %) multi-track and multi-layer prints; (iii) Inverse identification of optimal process parameters directly from customizable application objectives within 1–3 hours. We also validate the effectiveness of the AIDED experimentally by solving a multi-objective optimization problem to identify the optimal process parameters for achieving high print speeds with small effective track widths. Furthermore, we show the transferability of the framework from stainless steel to pure nickel using a small amount of additional data on pure nickel. With such transferability in AIDED, we pave a new way for “aiding” the process optimization of the laser-based AM processes that applies to a wide range of materials.
{"title":"Accurate inverse process optimization framework in laser directed energy deposition","authors":"Xiao Shang, Ajay Talbot, Evelyn Li, Haitao Wen, Tianyi Lyu, Jiahui Zhang, Yu Zou","doi":"10.1016/j.addma.2025.104736","DOIUrl":"10.1016/j.addma.2025.104736","url":null,"abstract":"<div><div>In additive manufacturing (AM), particularly in laser-based metal AM, process optimization is crucial to the quality of products and the efficiency of production. The identification of optimal process parameters out of a vast parameter space, however, is a daunting task. Despite advances in simulations, the process optimization for specific materials and geometries is developed through a sequential and time-consuming trial-and-error approach and often lacks the versatility to address multiple optimization objectives. Machine learning (ML) provides a powerful tool to accelerate the optimization process, but most current studies focus on simple single-track prints, which hardly translate to manufacturing 3D bulk components for engineering applications. In this study, we develop an <em>A</em>ccurate <em>I</em>nverse process optimization framework in laser <em>D</em>irected <em>E</em>nergy <em>D</em>eposition (AIDED), based on machine learning models and a genetic algorithm, to aid the process optimization in laser DED. Using AIDED, we demonstrate the following: (i) Accurate prediction of the area of single-track melt pool (<em>R</em><sup><em>2</em></sup> score 0.995), the tilt angle of multi-track melt pool (<em>R</em><sup><em>2</em></sup> score 0.969), and the cross-sectional geometries of multi-layer melt pool (1.75 % and 12.04 % errors in width and height, respectively) directly from process parameters; (ii) Determination of appropriate hatch spacing and layer thickness for fabricating fully dense (density > 99.9 %) multi-track and multi-layer prints; (iii) Inverse identification of optimal process parameters directly from customizable application objectives within 1–3 hours. We also validate the effectiveness of the AIDED experimentally by solving a multi-objective optimization problem to identify the optimal process parameters for achieving high print speeds with small effective track widths. Furthermore, we show the transferability of the framework from stainless steel to pure nickel using a small amount of additional data on pure nickel. With such transferability in AIDED, we pave a new way for “aiding” the process optimization of the laser-based AM processes that applies to a wide range of materials.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"102 ","pages":"Article 104736"},"PeriodicalIF":10.3,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143629526","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-10DOI: 10.1016/j.addma.2025.104734
Hong Seok Kim, Sang Hu Park
This study explores the performance of a replaceable alumina nozzle tip for directed energy deposition (DED), highlighting its advantages over traditional copper and brass nozzles, which are prone to high-temperature wear. Key innovations include a modular design for easy replacement of worn sections and the use of alumina, which provides superior resistance to mechanical, thermal, and chemical degradation, along with low laser absorption, making it ideal for prolonged high-temperature deposition. CFD simulations combined with a discrete phase model predict that alumina’s higher restitution coefficient (e) increases powder stream divergence and shifts the powder focus plane upward. High-speed camera observations confirmed that the alumina nozzle tip results in a wider powder spot size (∼26.1 %) and an elevated powder focus plane (∼19.3 %) compared to brass. Deposition experiments showed that the optimal substrate position for maximizing deposition height is well below the powder focus plane. To explain this, the study introduces powder incorporating efficiency (ηi), which, alongside powder focusing efficiency (ηf), significantly affects powder deposition efficiency (ηd), expressed as ηd = ηf × ηi. The alumina nozzle tip demonstrated a ∼5 % higher deposition height and ∼16 % lower nozzle tip temperatures compared to brass, making it suitable for high-powder-flow processes, such as high-deposition-rate DED and high-speed laser material deposition.
{"title":"Powder stream characteristics of replaceable alumina and brass nozzle tips for directed energy deposition","authors":"Hong Seok Kim, Sang Hu Park","doi":"10.1016/j.addma.2025.104734","DOIUrl":"10.1016/j.addma.2025.104734","url":null,"abstract":"<div><div>This study explores the performance of a replaceable alumina nozzle tip for directed energy deposition (DED), highlighting its advantages over traditional copper and brass nozzles, which are prone to high-temperature wear. Key innovations include a modular design for easy replacement of worn sections and the use of alumina, which provides superior resistance to mechanical, thermal, and chemical degradation, along with low laser absorption, making it ideal for prolonged high-temperature deposition. CFD simulations combined with a discrete phase model predict that alumina’s higher restitution coefficient (<em>e</em>) increases powder stream divergence and shifts the powder focus plane upward. High-speed camera observations confirmed that the alumina nozzle tip results in a wider powder spot size (∼26.1 %) and an elevated powder focus plane (∼19.3 %) compared to brass. Deposition experiments showed that the optimal substrate position for maximizing deposition height is well below the powder focus plane. To explain this, the study introduces powder incorporating efficiency (<em>η</em><sub><em>i</em></sub>), which, alongside powder focusing efficiency (<em>η</em><sub><em>f</em></sub>), significantly affects powder deposition efficiency (<em>η</em><sub><em>d</em></sub>), expressed as <em>η</em><sub><em>d</em></sub> = <em>η</em><sub><em>f</em></sub> × <em>η</em><sub><em>i</em></sub>. The alumina nozzle tip demonstrated a ∼5 % higher deposition height and ∼16 % lower nozzle tip temperatures compared to brass, making it suitable for high-powder-flow processes, such as high-deposition-rate DED and high-speed laser material deposition.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"102 ","pages":"Article 104734"},"PeriodicalIF":10.3,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143609198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Controlling internal defects within as-built parts is one of the great interests in the additive manufacturing field. In this study, we explore the powder spreading and defect evolution mechanisms on realistic printing surfaces through a comprehensive multiphysics simulation. The efficacy of a flat surface criterion for internal defect elimination was verified using a machine learning approach. The steady layer thickness in the electron beam melting process was estimated for different printing surfaces using the simulated powder bed density obtained through a high-fidelity discrete element method model. The steady layer thickness was greater on the flat printing surface compared to the rough surface due to high consolidation shrinkage. Monte-Carlo simulation revealed that electron backscattering is more pronounced on peaks of a rough surface than on a powder bed, due to the limited reabsorption of reflected electrons. The influence of the printing surface on melt pool stability and internal defect evolution was investigated using thermo-fluid dynamic simulations. Under identical process conditions, the molten pool surface exhibited greater stability on a rough printing surface than on a flat one, due to enhanced fluid flow. The flat printing surface resulted in lack of fusion defects < 100 μm in the external side region due to suppressed heat accumulation and a large steady layer thickness. Periodic deep valleys on rough surface can cause coarse defects < 200 μm in the external side region, as the melt pool depth is insufficient to match the increased local layer thickness in the valleys. Therefore, it was demonstrated that the printing surface must be considered to optimize outermost defects in as-built parts produced by the powder bed fusion electron beam melting process.
{"title":"Unveiling the influence of printing surfaces in powder bed fusion electron beam melting through multiphysics simulation","authors":"Seungkyun Yim , Tack Lee , Keiji Yanagihara , Kenta Aoyagi , Kenta Yamanaka , Akihiko Chiba","doi":"10.1016/j.addma.2025.104738","DOIUrl":"10.1016/j.addma.2025.104738","url":null,"abstract":"<div><div>Controlling internal defects within as-built parts is one of the great interests in the additive manufacturing field. In this study, we explore the powder spreading and defect evolution mechanisms on realistic printing surfaces through a comprehensive multiphysics simulation. The efficacy of a flat surface criterion for internal defect elimination was verified using a machine learning approach. The steady layer thickness in the electron beam melting process was estimated for different printing surfaces using the simulated powder bed density obtained through a high-fidelity discrete element method model. The steady layer thickness was greater on the flat printing surface compared to the rough surface due to high consolidation shrinkage. Monte-Carlo simulation revealed that electron backscattering is more pronounced on peaks of a rough surface than on a powder bed, due to the limited reabsorption of reflected electrons. The influence of the printing surface on melt pool stability and internal defect evolution was investigated using thermo-fluid dynamic simulations. Under identical process conditions, the molten pool surface exhibited greater stability on a rough printing surface than on a flat one, due to enhanced fluid flow. The flat printing surface resulted in lack of fusion defects < 100 μm in the external side region due to suppressed heat accumulation and a large steady layer thickness. Periodic deep valleys on rough surface can cause coarse defects < 200 μm in the external side region, as the melt pool depth is insufficient to match the increased local layer thickness in the valleys. Therefore, it was demonstrated that the printing surface must be considered to optimize outermost defects in as-built parts produced by the powder bed fusion electron beam melting process.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"102 ","pages":"Article 104738"},"PeriodicalIF":10.3,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143621445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-10DOI: 10.1016/j.addma.2025.104727
Lisa Freitag , Enrico Storti , Leif Bretschneider , Henning Zeidler , Jana Hubálková , Christos G. Aneziris
Spinel-based refractories were produced by binder jetting using a novel MgO-citric acid binder system and water as an activator of the acid–base reaction. Additionally to different amounts of binder and saturation levels, the addition of small amounts of PVA was investigated. Powder characteristics such as particle size distribution, particle shape and flowability as well as thermal behavior of the binder system were evaluated. Phase analysis by XRD conducted on dried and sintered samples indicated in situ spinel formation. Sintered samples exhibited low shrinkage ( 4%), but rather high apparent porosity ( 50 vol.%) and median pore size (). Compressive strength of dried and sintered samples was measured both parallel and perpendicular to the printed layers with values up to 8.5 MPa in the sintered state. After thermal shock with water, microcracks were formed and the residual strength was about 1.9 MPa. Selected sintered samples were analyzed with microfocused X-ray computed tomography, revealing the orientation of larger angular-shaped particles along the printed layers. Finally, a small crucible was successfully printed and sintered.
{"title":"Binder jetting of spinel-based refractory materials – processing, microstructure and properties","authors":"Lisa Freitag , Enrico Storti , Leif Bretschneider , Henning Zeidler , Jana Hubálková , Christos G. Aneziris","doi":"10.1016/j.addma.2025.104727","DOIUrl":"10.1016/j.addma.2025.104727","url":null,"abstract":"<div><div>Spinel-based refractories were produced by binder jetting using a novel MgO-citric acid binder system and water as an activator of the acid–base reaction. Additionally to different amounts of binder and saturation levels, the addition of small amounts of PVA was investigated. Powder characteristics such as particle size distribution, particle shape and flowability as well as thermal behavior of the binder system were evaluated. Phase analysis by XRD conducted on dried and sintered samples indicated in situ spinel formation. Sintered samples exhibited low shrinkage (<span><math><mo><</mo></math></span> <!--> <!-->4%), but rather high apparent porosity (<span><math><mo>></mo></math></span> <!--> <!-->50<!--> <!-->vol.%) and median pore size (<span><math><mrow><mo>></mo><mspace></mspace><mn>25</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span>). Compressive strength of dried and sintered samples was measured both parallel and perpendicular to the printed layers with values up to 8.5<!--> <!-->MPa in the sintered state. After thermal shock with water, microcracks were formed and the residual strength was about 1.9<!--> <!-->MPa. Selected sintered samples were analyzed with microfocused X-ray computed tomography, revealing the orientation of larger angular-shaped particles along the printed layers. Finally, a small crucible was successfully printed and sintered.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"102 ","pages":"Article 104727"},"PeriodicalIF":10.3,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143609426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-06DOI: 10.1016/j.addma.2025.104724
Subhadip Sahoo , Milad Khajehvand , Jason R. Mayeur , Kavan Hazeli
The rapid acceleration in materials discovery may overshadow the importance of thoroughly understanding the mechanical performance of newly developed materials in demanding environments. The recent interest in combining parametric studies with machine learning techniques to explore how changes in specific processing parameters or model inputs affect the overall behavior of a material system can only be truly beneficial if the governing constitutive relations describing material behavior are accurately established. In this study, we demonstrate the critical impact of accurately representing strut-level anisotropic material behavior in advanced stress analysis of additively manufactured lattice structures (AMLS). We introduce a systematic experimental and modeling approach for developing strut-level anisotropic elastoplastic material models that account for the influence of microstructural features such as porosity, texture, and surface roughness on the development of local anisotropic mechanical properties, which vary with strut orientation relative to the build direction (BD). As a result the presented material model captures and relates the statistics of spatially varying struts’ microstructural features to the local stress distribution. Our findings suggest that incorporating strut-level anisotropic material behavior into unit cell analysis significantly influences the load distribution and evolution of local stresses within the structure. Therefore, accounting for this anisotropy is critical for developing an understanding of unit cell behavior and performance, including subsequent topology/component design optimization based on this analysis.
{"title":"Critical impact of experimentally-driven strut level anisotropic material models in advanced stress analysis of additively manufactured lattice structures","authors":"Subhadip Sahoo , Milad Khajehvand , Jason R. Mayeur , Kavan Hazeli","doi":"10.1016/j.addma.2025.104724","DOIUrl":"10.1016/j.addma.2025.104724","url":null,"abstract":"<div><div>The rapid acceleration in materials discovery may overshadow the importance of thoroughly understanding the mechanical performance of newly developed materials in demanding environments. The recent interest in combining parametric studies with machine learning techniques to explore how changes in specific processing parameters or model inputs affect the overall behavior of a material system can only be truly beneficial if the governing constitutive relations describing material behavior are accurately established. In this study, we demonstrate the critical impact of accurately representing strut-level anisotropic material behavior in advanced stress analysis of additively manufactured lattice structures (AMLS). We introduce a systematic experimental and modeling approach for developing strut-level anisotropic elastoplastic material models that account for the influence of microstructural features such as porosity, texture, and surface roughness on the development of local anisotropic mechanical properties, which vary with strut orientation relative to the build direction (BD). As a result the presented material model captures and relates the statistics of spatially varying struts’ microstructural features to the local stress distribution. Our findings suggest that incorporating strut-level anisotropic material behavior into unit cell analysis significantly influences the load distribution and evolution of local stresses within the structure. Therefore, accounting for this anisotropy is critical for developing an understanding of unit cell behavior and performance, including subsequent topology/component design optimization based on this analysis.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"102 ","pages":"Article 104724"},"PeriodicalIF":10.3,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143576973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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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