Review
Chemistry, Physical
Kun Li, Tianbao Yang, Na Gong, Jinzhou Wu, Xin Wu, David Z. Zhang, Lawrence E. Murr
Summary: This paper reviews the research progress of additive manufacturing (AM) of ultra-high strength steels (UHSSs), focusing on defect optimization, microstructure-property regulation, and the application of advanced assisted techniques. The origin of UHSSs' mechanical properties and the characteristics of their forming microstructure using different AM techniques are discussed. The regulation methodology of UHSSs and the challenges for future development are also reviewed. This work is important for a better scientific understanding and vital guidelines for UHSSs manufacturing in the future.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Chemistry, Physical
Matthias Droste, Ruben Wagner, Johannes Guenther, Christina Burkhardt, Sebastian Henkel, Thomas Niendorf, Horst Biermann
Summary: The austenitic steel processed by electron beam powder bed fusion (PBF-EB) exhibits a robust cyclic crack growth behavior, with minimal influence from microstructure and building direction.
Article
Nanoscience & Nanotechnology
Feifan Fan, Mingguang Jiang, Pei Wang, Changyong Liu, Zhiyuan Liu, Zhangwei Chen
Summary: Previous research has focused on improving mechanical properties through heterogenous microstructure modification, but the evolution of microstructure during deformation involving metallurgical defects has not been clarified. This study investigated the additive manufacturing of austenitic 316L stainless steel and revealed the competitive plastic deformation mechanisms and microstructural changes. The findings provide important guidance for the development of high strength and ductile stainless steels through additive manufacturing.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2022)
Article
Materials Science, Multidisciplinary
E. R. Lewis, M. P. Taylor, B. Attard, N. Cruchley, A. P. C. Morrison, M. M. Attallah, S. Cruchley
Summary: The oxidation behavior of Laser Powder Bed Fused (L-PBF) IN625 was studied in both as-built and heat-treated conditions. Recrystallization with twin grain boundaries and Nb-rich carbides decorated grain boundaries were observed after heat treatment. Exposure of L-PBF IN625 samples in laboratory air at 950 degrees C led to the formation of an external chromia scale and a near-continuous 6-phase layer at the scale/alloy boundary. The oxidation kinetics were similar to wrought IN625, but exhibited a more cubic behavior likely due to the formation of the 6-phase layer.
Article
Materials Science, Coatings & Films
L. M. Kang, S. Q. Xu, Y. K. Bai, Y. F. Qiu, X. Pang, J. M. Zheng, X. C. Luo, H. L. Liu, B. C. Xian, C. Yang
Summary: With the development of science and technology and the popularization of intelligent manufacturing, laser additive manufacturing of titanium alloys is being considered in industrial adoption due to its advantages. However, large scale columnar crystals formed in the as-prepared alloy result in anisotropic macroscopic properties. In this study, a dual laser processing technique integrating laser melting deposition and laser shock peening was proposed to achieve isotropic microstructure in Ti-6Al-4V alloy, providing insight into fabricating isotropic metal components with higher performance.
SURFACE & COATINGS TECHNOLOGY
(2023)
Article
Engineering, Manufacturing
Pengfei He, Zhengying Wei, Yongchao Wang, Minbo Jiang, Chen Ma, Xueli Chen, Xuhui Lai
Summary: In this paper, a novel droplet + arc additive manufacturing (DAAM) method was proposed for building high quality and high efficiency aluminum alloy components. A special droplet generation system (DGS) was designed to replace the traditional wire feeding system, allowing the material addition process and the arc heat input process to function independently. The experimental results demonstrated that the DAAM process improved the continuity of the deposition process and significantly reduced the harmful impact of droplets on the molten pool. In addition, the DAAM process showed great inclusiveness of droplet falling deviation and successfully fabricated multi-layer thin-wall components and ring-shaped structures.
ADDITIVE MANUFACTURING
(2023)
Article
Materials Science, Multidisciplinary
Lixia Xi, Juncan Xu, Dongdong Gu, Lili Feng, Qiuyang Lu, Konda Gokuldoss Prashanth
Summary: In this study, 2195 Al-Li alloys and 2195-Ti/CeB6 composites were manufactured and compared at relatively high scan speeds to investigate the effect of Ti/CeB6 on crack inhibition and mechanical properties. The addition of Ti/CeB6 significantly refined the grains of the 2195 alloys, reducing their size by one order of magnitude. The 2195-Ti/CeB6 composites showed good laser processability without cracks at high scan speeds. The composites exhibited a high tensile strength of 300 MPa and elongation of 5.5%, increasing by 33% and 35% respectively compared to crack-free alloys at low scan speeds. This study provides references for crack suppression in laser additive manufacturing of high-crack-susceptibility metallic alloys.
Article
Chemistry, Physical
Hari Venkit, Senthil Kumaran Selvaraj
Summary: This work analyzes a novel solid-state manufacturing approach of a friction stir additive manufacturing (FSAM) technique for fabricating multiple layers of alternating gradient composite structure. The study found nonuniform microstructures along the build direction, with the nugget zone having fine equiaxed grains. Grain sizes and precipitate sizes were affected by the varying thermal cycles created by the tool, resulting in increased strength and hardness from the lower layer to the upper layer of the FSAM build. The findings suggest that FSAM can be used to fabricate defect-free large structures with expected mechanical characteristics, serving as a suitable substitute for conventional automobile components.
Article
Engineering, Mechanical
Mattia Mele, Giampaolo Campana, Gian Luca Monti
Summary: The study proposes a solution to avoid the capillarity effect in MJF by inducing it outside of the part under construction. This approach involves adding a fin-shaped appendage to the top surface, similar to risers in foundry technology, which has shown satisfactory results in experimental measurements. Future developments are planned to further refine the design.
RAPID PROTOTYPING JOURNAL
(2021)
Article
Engineering, Manufacturing
Lei Zhang, Qingping Ma, Junhao Ding, Shuo Qu, Jin Fu, Ming Wang Fu, Xu Song, Michael Yu Wang
Summary: Additively manufactured elastically isotropic lattice structures are promising for lightweight structural applications. However, the layer-by-layer construction in additive manufacturing often leads to undesired anisotropy in fabricated materials. In this work, a design method using variable thickness triply periodic minimal surface (TPMS) shell lattices is proposed to achieve elastic isotropy from anisotropic constitutive materials. The method utilizes a gradient-based optimization approach and the universal anisotropy index as the objective, allowing for the design of any orthotropic lattice.
ADDITIVE MANUFACTURING
(2022)
Article
Chemistry, Multidisciplinary
Fernando Senhora, Emily D. Sanders, Glaucio H. Paulino
Summary: Spinodal architected materials optimize design of multiscale structures by varying spinodal class, orientation, and porosity, leading to efficient material placement along stress trajectories with enhanced mechanical and biological functions.
ADVANCED MATERIALS
(2022)
Article
Construction & Building Technology
Dong Cui, Yingxuan Wu, Xiaoying Xie, Guanfei Tian, Guantong Han, Yi Wan, Keren Zheng, Wenting Li
Summary: The microstructure of a 3D-printed mortar was investigated in this study. A novel leaching strategy was used to enhance the density contrast between sand and cementitious slurry, allowing for the spatial dispersion of sands in 3D-printed mortar. X-ray attenuation method (XRAM) was introduced to investigate the spatial distribution of local porosity. The research results provide a deeper understanding of 3D-printed concrete.
JOURNAL OF SUSTAINABLE CEMENT-BASED MATERIALS
(2023)
Article
Engineering, Mechanical
C. Boursier Niutta, A. Tridello, G. Barletta, N. Gallo, A. Baroni, F. Berto, D. S. Paolino
Summary: This paper proposes a generalized formulation of defect-driven topology optimization (TO) for fatigue design, named TopFat. The proposed method limits the first principal stress in accordance with the defect size distribution of the additive manufacturing process. The results show that considering the defect population significantly affects the final topology and leads to feasible optimum solutions.
ENGINEERING FAILURE ANALYSIS
(2022)
Article
Materials Science, Multidisciplinary
Devin P. Anderson, Keith J. Billings, Andre M. Pate, John Paul C. Borgonia, Samad A. Firdosy, Gerald E. Voecks, Erik J. Brandon, William C. West
Summary: This article discusses the use of topology optimization to design lightweight end plates for water electrolyzers. By reducing the weight and volume of the end plates, the performance of the electrolyzer can be improved. The study finds that with topology optimization and additive manufacturing, it is possible to design and fabricate end plates for high-pressure electrolysis systems with significant decreases in mass and volume.
JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE
(2022)
Review
Materials Science, Multidisciplinary
Wei Zhang, Ali Chabok, Bart J. Kooi, Yutao Pei
Summary: This article summarizes the microstructure characteristics, mechanical properties, and functional properties of additive manufactured high entropy alloys (HEAs), providing a fundamental understanding of this research field. The article also discusses the current challenges and future work in this area.
MATERIALS & DESIGN
(2022)
Article
Physiology
Kathleen Cantow, Thomas Gladytz, Jason M. Millward, Sonia Waiczies, Thoralf Niendorf, Erdmann Seeliger
Summary: This study used dynamic MRI to monitor kidney size and provided physiological interpretation of changes in renal oxygenation. The results showed correlations between changes in kidney size and T-2* and T-2. Monitoring kidney size allows for a better understanding of renal pathophysiology.
Article
Materials Science, Multidisciplinary
Johanna-Maria Frenck, Malte Vollmer, Thomas Niendorf
Summary: This study investigates the corrosion behavior of a Fe-Mn-Al-Ni-Cr shape memory alloy in a 5.0 wt% NaCl solution and its functional properties. The addition of chromium improves corrosion resistance, but the alloy still exhibits unstable passive behavior in the single crystalline condition.
MATERIALS AND CORROSION-WERKSTOFFE UND KORROSION
(2023)
Article
Materials Science, Multidisciplinary
Guney Guven Yapici, Seyed Vahid Sajadifar, Ali Hosseinzadeh, Thomas Wegener, Cesar Sobrero, Anna Engelhardt, Thomas Niendorf
Summary: In this study, the cyclic mechanical behavior of AZ31 magnesium alloy after multipass friction stir processing (FSP) is investigated up to the very high-cycle fatigue (VHCF) regime. The grain refinement and texture evolution after processing are evaluated to enhance the understanding of the fatigue response. The friction stir processed AZ31 shows increased ultimate tensile strength and ductility, but its fatigue performance deteriorates due to low yield strength and texture evolution after processing.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Automation & Control Systems
Marco Sode, Moritz Kahlert, Tizian Arold, Adam Peter Fros, Malte Vollmer, Thomas Niendorf, Martin Fehlbier
Summary: Additive manufacturing (AM) has the potential to influence heat transfer in high-pressure die casting (HPDC) and reduce the cycle time of the process. This study investigates the impact of metallic static mixers on fluid dynamics and heat transfer in HPDC using experimental and computational fluid dynamics (CFD) simulation. The results show that metallic static mixers can enhance heat transfer and improve the efficiency of the HPDC process.
INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY
(2023)
Article
Engineering, Mechanical
Julia Richter, Christof Johannes Jaime Torrent, Marcel Krochmal, Thomas Wegener, Malte Vollmer, Thomas Niendorf
Summary: Gas-atomized (GA) and water-atomized (WA) commercially pure iron (cp-Fe) powders were processed using laser-based powder bed fusion, resulting in slightly higher porosity for the WA condition. Fatigue tests, which are negatively affected by porosity, also showed good properties for the WA condition. The microstructure stability significantly differed between the GA and WA specimens and can be explained based on chemical composition. The GA specimens exhibited yield phenomenon and softening under cyclic loading, while the WA specimens maintained microstructure stability in cyclic tests.
INTERNATIONAL JOURNAL OF FATIGUE
(2023)
Article
Nanoscience & Nanotechnology
R. Lehnert, M. Mueller, M. Vollmer, P. Krooss, G. Korpala, U. Prahl, M. Wendler, O. Volkova, T. Niendorf, H. Biermann, A. Weidner
Summary: The superelasticity of iron-based shape memory alloys is affected by microstructural features and elementary processes like dislocation formation and interaction, leading to functional degradation. In situ characterization techniques such as digital image correlation and infrared thermography, along with ex situ high resolution electron backscatter diffraction and electron contrast channeling imaging, were used to study the functional stability of Fe-Mn-Al-Ni alloys under loading. The early stabilization of martensite during repeated loading was attributed to the interaction of different martensite variants and the formation of dislocations.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2023)
Article
Chemistry, Physical
Maximilian Schleiting, Alexander Wetzel, Andre Bauer, Johanna-Maria Frenck, Thomas Niendorf, Bernhard Middendorf
Summary: A prestressing method using Fe-Mn-Al-Ni shape memory alloy rebars is investigated in this work. The stress of about 130 MPa is achieved for the novel rebars, and an improvement in maximum flexural strength and rigidity is observed compared to non-activated rebars. Future research should focus on the design and construction applications of the shape memory alloy rebars, as well as the long-term performance of the prestressing system.
Article
Materials Science, Multidisciplinary
Christoph Ostwald, Manuel Opfer, Cyril Popov, Thomas Niendorf
Summary: The hot forming process in the automotive industry produces high-strength structural components. However, these materials are susceptible to hydrogen embrittlement. The heat treatment during the process introduces diffusible hydrogen into boron-manganese steels with aluminum-silicon coating. This study investigated the influence of process gases and furnace dwell times on hydrogen uptake, revealing that nitrogen and carbon dioxide gases resulted in higher hydrogen absorption compared to synthetic air and oxygen.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)
Article
Materials Science, Multidisciplinary
M. Vollmer, S. Degener, A. Bolender, A. Bauer, A. Liehr, A. Stark, N. Schell, P. Barriobero-Vila, G. Requena, T. Niendorf
Summary: A recently developed strategy for promoting abnormal grain growth during cyclic heat treatment has the potential to manufacture single crystals with a size of several centimeters. However, there is still a lack of detailed understanding of the elementary mechanisms involved in this kind of abnormal grain growth. This study provides time resolved insights into the interplay of these mechanisms for the first time, using in situ synchrotron high energy X-ray diffraction analysis. The results not only deepen our understanding of abnormal grain growth, but also lay the foundation for improving the efficiency of the cyclic heat treatment process and obtaining even larger single crystals.
Article
Materials Science, Multidisciplinary
Johanna-Maria Frenck, Janna Link, Malte Vollmer, Thomas Niendorf
Summary: The electrochemical corrosion properties of Fe-Mn-Al-Ni in different electrolytic solutions were investigated by measuring the open circuit potential and conducting potentiodynamic polarization measurements. The results showed that exposure to a high pH (=13.3) solution resulted in passive behavior. However, the addition of Cl- ions to the solution changed the corrosion behavior from passivating to non-passivating. Optical microscopy images revealed selective corrosion of the beta-Mn-phase or the gamma'-phase, regardless of the electrolytic solution.
Article
Nanoscience & Nanotechnology
Aravindh Nammalvar Raja Rajan, Marcel Krochmal, Mahdieh Shahmardani, Thomas Wegener, Alexander Hartmaier, Thomas Niendorf, Ghazal Moeini
Summary: The AM process continues to attract attention in industrial and academic research due to its high degrees of design freedom and flexibility in the production process. However, the use of AM-processed components for parts under cyclic loading is limited by significant variance in cyclic behavior and the effects of AM-associated defects. This study examines and predicts the low-cycle fatigue behavior of AlSi10Mg parts produced by laser-based powder bed fusion in both the as-built and direct-aged condition using experiments and microstructure-sensitive models. The applied modeling framework accurately predicts the LCF behavior of AlSi10Mg under various strain amplitudes and ratios for both conditions.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2023)
Article
Engineering, Civil
Zhen-Yu Chen, Xiang-Lin Gu, Malte Vollmer, Thomas Niendorf, Elyas Ghafoori, Qian-Qian Yu
Summary: This paper investigates the mechanical properties and recovery stress behavior of an iron-based shape memory alloy (Fe-SMA), focusing on the effects of fatigue and thermal loading. The recovery stress change of activated Fe-SMAs subjected to fatigue at different temperatures was monitored, and the retrievability of the lost recovery stress was studied. Coefficients of thermal expansion (CTEs) were also calculated for samples with different activation histories. The results show that the maximum reduction in recovery stress after two million cyclic loads was around 20% at room temperature and -20°C, but only 10% at 60°C. However, the lost recovery stress due to fatigue could be effectively retrieved by a reactivation regardless of the temperature scenarios.
THIN-WALLED STRUCTURES
(2023)
Article
Radiology, Nuclear Medicine & Medical Imaging
Carl J. J. Herrmann, Ludger Starke, Jason M. Millward, Joseph Kuchling, Friedemann Paul, Thoralf Niendorf
Summary: Accelerated T-2 and T-2* mapping using highly undersampled 2in1-RARE-EPI with compressed sensing (CS) reconstruction is feasible. The results show that for R-extra = 6, the overall MAPE for T-2* is <= 8% and <= 4% for T-2; for R-extra = 12, the overall MAPE is <13% for T-2* and <5% for T-2.
Article
Medicine, Research & Experimental
Ludger Starke, Jason M. Millward, Christian Prinz, Fatima Sherazi, Helmar Waiczies, Christoph Lippert, Marc Nazare, Friedemann Paul, Thoralf Niendorf, Sonia Waiczies
Summary: The study demonstrates that siponimod can be imaged non-invasively using 19F UTE MRI, laying the foundation for further preclinical and clinical investigations. This technique provides an accurate understanding of the distribution of CNS-acting drugs in individual patients, which can contribute to personalized therapy.
Article
Materials Science, Multidisciplinary
N. Sommer, S. Lee, F. Stredak, C. Wolf, A. Suckau, M. Vollmer, S. Shao, T. Niendorf, N. Shamsaei, S. Boehm
Summary: The dynamic deformation behavior of metallic materials is crucial for crash-safe design in various applications. However, there has been limited research on the dynamic deformation properties in additive manufacturing. This study provides a comprehensive overview of the dynamic tensile deformation properties of AISI 316L stainless steel fabricated by laser-beam directed energy deposition. The study examines the interrelationships of process parameters, post-process heat treatments, and resulting microstructure. The findings show that the active deformation mechanisms and fracture elongations are influenced by heat treatment and microstructural effects.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)