Additive Manufacturing of Architected Metallic Materials

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Additive Manufacturing".

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 14927

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Delft University of Technology (TU Delft), Mekelweg 2, Delft 2628CD, The Netherlands
Interests: 3D/ 4D printing; biomaterials; biomimetics; multifunctional materials; designer materials; functionally graded materials; biomechanics
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Special Issue Information

Dear Colleagues,

Metal additive manufacturing (AM, also known as 3D printing) is used for the fabrication of three-dimensional materials made from metals and their alloys. The layer-upon-layer nature of AM techniques makes it possible to create metallic structures with complex cellular architectures, which are often to some extent similar to those found in natural materials. The free-form competence of AM techniques, when combined with printing of multiple materials at the same time, provides a unique opportunity for the fabrication of architected materials with tailor-made functionalities and (mechanical) properties. Such architected metallic materials have numerous high-tech applications in high added value industries, such as healthcare and mobility. This Special Issue, therefore, aims to present the latest research related to the design and fabrication of 3D-printed architected metallic materials. It also covers the advances in their characterization, (post-)processing, computational modeling (e.g., topology optimization, failure analysis), and applications particularly in the area of biomedical engineering (e.g., orthopedic implants).

Dr. Mohammad J. Mirzaali
Prof. Dr. Amir A. Zadpoor
Guest Editors

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Keywords

  • Metallic additive manufacturing
  • Architected materials
  • Functional gradient
  • Designer materials
  • Biomimetics

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Published Papers (4 papers)

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Research

20 pages, 9029 KiB  
Article
External Illumination Enables Coaxial Sensing of Surface and Subsurface Molten Pool Geometry in LPBF
by Leonardo Caprio, Ali Gökhan Demir and Barbara Previtali
Metals 2022, 12(10), 1762; https://doi.org/10.3390/met12101762 - 20 Oct 2022
Cited by 3 | Viewed by 2257
Abstract
Laser powder bed fusion (LPBF) attracts the attention of high-end manufacturing sectors for its capability of depositing free-form components with elevated mechanical properties. However, due to the intrinsic nature of the feedstock material and the interaction with the laser beam, the process is [...] Read more.
Laser powder bed fusion (LPBF) attracts the attention of high-end manufacturing sectors for its capability of depositing free-form components with elevated mechanical properties. However, due to the intrinsic nature of the feedstock material and the interaction with the laser beam, the process is prone to defect formation and manufacturing inaccuracies. Therefore, the development of a monitoring architecture capable of measuring the geometrical features of the process tool (i.e., the melt pool generated by the laser-material interaction) is of paramount importance. This information may then be exploited to evaluate process stability. In this work, a high-speed camera was implemented coaxially in the optical chain of an LPBF system to extrapolate the geometrical features of the molten pool surface and its oscillatory behaviour, with elevated spatial and temporal resolution. A secondary light source was tested in both coaxial and off-axis configuration to dominate process emission and assess optimal illumination conditions for extracting the molten pool’s geometrical features. Preliminary results showed that the off-axis configuration of the illumination light enabled direct measurement of the molten pool surface geometry. A newly developed image processing algorithm based on illuminated images obtained via the coaxial observation frame was employed to provide automated identification of the melt pool geometry. Moreover, bright reflections of the external illumination over the melt surface could be clearly observed and used to characterise the oscillatory motion of the molten material. This information may therefore be taken as an indirect indicator of the molten pool penetration depth, hence providing information regarding the subsurface geometry. A successive experimental investigation showed the capability of the monitoring architecture to resolve the molten pool’s length, width and area with elevated acquisition frequency. Molten pool surface oscillations in the kHz range could be correlated to the penetration depth while the molten pool width measured via the high-speed imaging setup corresponded to the track width of the depositions. Hence, the methodological approach for the concurrent measurement of the molten pool’s geometry in three spatial dimensions was demonstrated and may be used to track the stability of LPBF depositions. Full article
(This article belongs to the Special Issue Additive Manufacturing of Architected Metallic Materials)
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17 pages, 13099 KiB  
Article
Programmed Plastic Deformation in Mathematically-Designed Architected Cellular Materials
by Oraib Al-Ketan
Metals 2021, 11(10), 1622; https://doi.org/10.3390/met11101622 - 13 Oct 2021
Cited by 13 | Viewed by 5659
Abstract
The ability to control the exhibited plastic deformation behavior of cellular materials under certain loading conditions can be harnessed to design more reliable and structurally efficient damage-tolerant materials for crashworthiness and protective equipment applications. In this work, a mathematically-based design approach is proposed [...] Read more.
The ability to control the exhibited plastic deformation behavior of cellular materials under certain loading conditions can be harnessed to design more reliable and structurally efficient damage-tolerant materials for crashworthiness and protective equipment applications. In this work, a mathematically-based design approach is proposed to program the deformation behavior of cellular materials with minimal surface-based topologies and ductile constituent material by employing the concept of functional grading to control the local relative density of unit cells. To demonstrate the applicability of this design tactic, two examples are presented. Rhombic, and double arrow deformation profiles were programmed as the desired deformation patterns. Grayscale images were used to map the relative density distribution of the cellular material. 316L stainless steel metallic samples were fabricated using the powder bed fusion additive manufacturing technique. Results of compressive tests showed that the designed materials followed the desired programmed deformation behavior. Results of mechanical testing also showed that samples with programmed deformation exhibited higher plateau stress and toughness values as compared to their uniform counterparts while no effect on Young’s modulus was observed. Plateau stress values increased by 8.6% and 13.4% and toughness values increased by 5.6% and 11.2% for the graded-rhombic and graded-arrow patterns, respectively. Results of numerical simulations predicted the exact deformation behavior that was programmed in the samples and that were obtained experimentally. Full article
(This article belongs to the Special Issue Additive Manufacturing of Architected Metallic Materials)
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20 pages, 112952 KiB  
Article
Experimental Investigation and Comparison of the Thermal Performance of Additively and Conventionally Manufactured Heat Exchangers
by Ana Vafadar, Ferdinando Guzzomi and Kevin Hayward
Metals 2021, 11(4), 574; https://doi.org/10.3390/met11040574 - 1 Apr 2021
Cited by 12 | Viewed by 2844
Abstract
Air heat exchangers (HXs) are applicable in many industrial sectors because they offer a simple, reliable, and cost-effective cooling system. Additive manufacturing (AM) systems have significant potential in the construction of high-efficiency, lightweight HXs; however, HXs still mainly rely on conventional manufacturing (CM) [...] Read more.
Air heat exchangers (HXs) are applicable in many industrial sectors because they offer a simple, reliable, and cost-effective cooling system. Additive manufacturing (AM) systems have significant potential in the construction of high-efficiency, lightweight HXs; however, HXs still mainly rely on conventional manufacturing (CM) systems such as milling, and brazing. This is due to the fact that little is known regarding the effects of AM on the performance of AM fabricated HXs. In this research, three air HXs comprising of a single fin fabricated from stainless steel 316 L using AM and CM methods—i.e., the HXs were fabricated by both direct metal printing and milling. To evaluate the fabricated HXs, microstructure images of the HXs were investigated, and the surface roughness of the samples was measured. Furthermore, an experimental test rig was designed and manufactured to conduct the experimental studies, and the thermal performance was investigated using four characteristics: heat transfer coefficient, Nusselt number, thermal fluid dynamic performance, and friction factor. The results showed that the manufacturing method has a considerable effect on the HX thermal performance. Furthermore, the surface roughness and distribution, and quantity of internal voids, which might be created during and after the printing process, affect the performance of HXs. Full article
(This article belongs to the Special Issue Additive Manufacturing of Architected Metallic Materials)
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12 pages, 5278 KiB  
Article
Surface Modification of the EBM Ti-6Al-4V Alloy by Pulsed Ion Beam
by Natalia Pushilina, Ekaterina Stepanova, Andrey Stepanov and Maxim Syrtanov
Metals 2021, 11(3), 512; https://doi.org/10.3390/met11030512 - 19 Mar 2021
Cited by 11 | Viewed by 2734
Abstract
The effect of surface modification of Ti-6Al-4V samples manufactured by electron beam melting (EBM) using a pulsed carbon ion beam is studied in the present work. Based on the results of XRD, SEM, and TEM analysis, patterns of changes in the microstructure and [...] Read more.
The effect of surface modification of Ti-6Al-4V samples manufactured by electron beam melting (EBM) using a pulsed carbon ion beam is studied in the present work. Based on the results of XRD, SEM, and TEM analysis, patterns of changes in the microstructure and phase composition of the EBM Ti-6Al-4V alloy, depending on the number of pulses of pulsed ion beam exposure, are revealed. It was found that gradient microstructure is formed as a result of pulsed ion beam irradiation of the EBM Ti-6Al-4V samples. The microstructure of the surface layer up to 300 nm thick is represented by the (α + α”) phase. At depths of 0.3 μm, the microstructure is mixed and contains alpha-phase plates and needle-shaped martensite. The mechanical properties were investigated using methods of uniaxial tensile tests, micro- and nanohardness measurements, and tribological tests. It was shown that surface modification by a pulsed ion beam at an energy density of 1.92 J/cm2 and five pulses leads to an increase in the micro- and nanohardness of the surface layers, a decrease in the wear rate, and a slight rise in the plasticity of EBM Ti-6Al-4V alloy. Full article
(This article belongs to the Special Issue Additive Manufacturing of Architected Metallic Materials)
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