Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
4.4
2.9
Journals
Metals
Special Issues
Metal Additive Manufacturing – State of the Art 2020
share announcement

Metal Additive Manufacturing – State of the Art 2020

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

Deadline for manuscript submissions: closed (31 January 2021) | Viewed by 56468

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Nader Asnafi

E-Mail Website
Guest Editor
School of Science and Technology, Örebro University, SE-701 82 Örebro, Sweden
Interests: digital transformation; materials and technologies for a circular economy; development and operation/use of sustainable products and manufacturing systems
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Additive manufacturing (AM), more popularly known as 3D printing, comprises a group of technologies used to produce objects through the addition (rather than removal) of material. AM is used in many industries—aerospace and defense, automotive, consumer products, industrial products, medical devices, and architecture. AM is transforming the industry, and this industrial transformation is expected to become more comprehensive and reach a higher pace during the coming years.

Additive manufacturing of metal components with virtually no geometric limitations has enabled new product design options and opportunities, increased product performance, shorter cycle time in part production, total cost reduction, shortened lead time, improved material efficiency, more sustainable products and processes, full circularity in the economy, and new revenue streams.

This Special Issue of Metals focuses on metal additive manufacturing with respect to the topics mentioned below (please see the Keywords/Topics below). The papers presented in this Special Issue give an account of the 2020 scientific, technological, and industrial state of the art for metal additive manufacturing from different perspectives (see the Keywords/Topics below). Your contribution to this 2020 account is highly valuable and appreciated.

Prof. Dr. Nader Asnafi
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

The submitted contribution should address metal additive manufacturing with respect to one or several of the following topics:
  • Business models and engineering
  • Product/component design (including generative design, topology optimization, lattice and surface optimization, etc.)
  • Industrial applications (aerospace, defense, automotive, consumer, medical, and industrial products, etc.)
  • Material and process design and engineering
  • New materials
  • Powder production and characterization
  • Systems and equipment engineering
  • Post-processing
  • Process control and optimization and quality assurance

Published Papers (12 papers)

Download All Papers
Order results
Result details
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:

Editorial

Jump to: Research, Review

3 pages, 178 KiB  
Editorial
Metal Additive Manufacturing—State of the Art 2020
by Nader Asnafi
Metals 2021, 11(6), 867; https://doi.org/10.3390/met11060867 - 26 May 2021
Cited by 6 | Viewed by 2813
Abstract
Additive manufacturing (AM), more popularly known as 3D printing, comprises a group of technologies used to produce objects through the addition (rather than the removal) of material [...] Full article
(This article belongs to the Special Issue Metal Additive Manufacturing – State of the Art 2020)

Research

Jump to: Editorial, Review

15 pages, 5166 KiB  
Article
Additive Manufactured 316L Stainless-Steel Samples: Microstructure, Residual Stress and Corrosion Characteristics after Post-Processing
by Suvi Santa-aho, Mika Kiviluoma, Tuomas Jokiaho, Tejas Gundgire, Mari Honkanen, Mari Lindgren and Minnamari Vippola
Metals 2021, 11(2), 182; https://doi.org/10.3390/met11020182 - 20 Jan 2021
Cited by 23 | Viewed by 4032
Abstract
Additive manufacturing (AM) is a relatively new manufacturing method that can produce complex geometries and optimized shapes with less process steps. In addition to distinct microstructural features, residual stresses and their formation are also inherent to AM components. AM components require several post-processing [...] Read more.
Additive manufacturing (AM) is a relatively new manufacturing method that can produce complex geometries and optimized shapes with less process steps. In addition to distinct microstructural features, residual stresses and their formation are also inherent to AM components. AM components require several post-processing steps before they are ready for use. To change the traditional manufacturing method to AM, comprehensive characterization is needed to verify the suitability of AM components. On very demanding corrosion atmospheres, the question is does AM lower or eliminate the risk of stress corrosion cracking (SCC) compared to welded 316L components? This work concentrates on post-processing and its influence on the microstructure and surface and subsurface residual stresses. The shot peening (SP) post-processing levelled out the residual stress differences, producing compressive residual stresses of more than −400 MPa in the AM samples and the effect exceeded an over 100 µm layer below the surface. Post-processing caused grain refinement and low-angle boundary formation on the sample surface layer and silicon carbide (SiC) residue adhesion, which should be taken into account when using the components. Immersion tests with four-point-bending in the heated 80 °C magnesium chloride solution for SCC showed no difference between AM and reference samples even after a 674 h immersion. Full article
(This article belongs to the Special Issue Metal Additive Manufacturing – State of the Art 2020)
►▼ Show Figures

Figure 1

11 pages, 4230 KiB  
Article
Process Window for Electron Beam Melting of 316LN Stainless Steel
by Stefan Roos and Lars-Erik Rännar
Metals 2021, 11(1), 137; https://doi.org/10.3390/met11010137 - 12 Jan 2021
Cited by 12 | Viewed by 2466
Abstract
Electron beam melting (EBM) is currently hampered by the low number of materials available for processing. This work presents an experimental study of process parameter development related to EBM processing of stainless steel alloy 316LN. Area energy (AE) input and beam deflection rate [...] Read more.
Electron beam melting (EBM) is currently hampered by the low number of materials available for processing. This work presents an experimental study of process parameter development related to EBM processing of stainless steel alloy 316LN. Area energy (AE) input and beam deflection rate were varied to produce a wide array of samples in order to determine which combination of process parameters produced dense (>99%) material. Both microstructure and tensile properties were studied. The aim was to determine a process window which results in dense material. The range of AE which produced dense materials was found to be wider for 316LN than for many other reported materials, especially at lower beam deflection rates. Tensile and microstructural analysis showed that increasing the beam deflection rate, and consequently lowering the AE, resulted in material with a smaller grain size, lower ductility, lower yield strength, and a narrower window for producing material that is neither porous nor swelling. Full article
(This article belongs to the Special Issue Metal Additive Manufacturing – State of the Art 2020)
►▼ Show Figures

Graphical abstract

11 pages, 4661 KiB  
Article
Effects of Thermal Cycling on Wire and Arc Additive Manufacturing of Al-5356 Components
by Markus Köhler, Jonas Hensel and Klaus Dilger
Metals 2020, 10(7), 952; https://doi.org/10.3390/met10070952 - 15 Jul 2020
Cited by 31 | Viewed by 4245
Abstract
Wire and arc additive manufacturing (WAAM) provides a promising alternative to conventional machining for the production of large structures with complex geometry, as well as individualized low quantity components, using cost-efficient production resources. Due to the layer-by-layer build-up approach, process conditions, such as [...] Read more.
Wire and arc additive manufacturing (WAAM) provides a promising alternative to conventional machining for the production of large structures with complex geometry, as well as individualized low quantity components, using cost-efficient production resources. Due to the layer-by-layer build-up approach, process conditions, such as energy input, deposition patterns and heat conduction during the additive manufacturing process result in a unique thermal history of the structure, affecting the build-up properties. This experimental study aims to describe the effects of thermal cycling on the geometrical and material properties of wire arc additive manufactured Al-5356 aluminum alloy. Under consideration, that Al-5356 is a non-heat treatable alloy, a significant effect on geometrical formation is expected. Linear wall samples were manufactured using pulsed cold metal transfer (CMT-P) under variation of wire-feed rate, travel speed and interpass temperatures. The samples were analyzed in terms of geometry; microstructural composition; hardness and residual stress. Furthermore, the mechanical properties were determined in different building directions. Full article
(This article belongs to the Special Issue Metal Additive Manufacturing – State of the Art 2020)
►▼ Show Figures

Figure 1

14 pages, 4997 KiB  
Article
Development of a High Strength Magnesium Alloy for Wire Arc Additive Manufacturing
by Stefan Gneiger, Johannes A. Österreicher, Aurel R. Arnoldt, Alois Birgmann and Martin Fehlbier
Metals 2020, 10(6), 778; https://doi.org/10.3390/met10060778 - 10 Jun 2020
Cited by 31 | Viewed by 5111
Abstract
Due to their high specific strength, magnesium alloys are promising materials for further lightweighting in mobility applications. In contrast to casting and forming processes, additive manufacturing methods allow high degrees of geometrical freedom and can generate significant weight reductions due to load-specific part [...] Read more.
Due to their high specific strength, magnesium alloys are promising materials for further lightweighting in mobility applications. In contrast to casting and forming processes, additive manufacturing methods allow high degrees of geometrical freedom and can generate significant weight reductions due to load-specific part design. In wire arc additive manufacturing processes, large parts can be produced with high material utilization. Process-inherent high melt temperatures and solidification rates allow for the use of magnesium alloys which are otherwise complicated to process; this enables the use of unconventional alloying systems. Here, we report the development of a Mg-Al-Zn-Ca-rare earth alloy for wire arc additive manufacturing (WAAM). Compared to parts made of commercially available filler wire, the newly developed alloy achieves a higher strength (approx. +9 MPa yield strength, +25 MPa ultimate tensile strength) in WAAM. Full article
(This article belongs to the Special Issue Metal Additive Manufacturing – State of the Art 2020)
►▼ Show Figures

Figure 1

11 pages, 4819 KiB  
Article
Thermal Frequency Drift of 3D Printed Microwave Components
by Gregory Peter Le Sage
Metals 2020, 10(5), 580; https://doi.org/10.3390/met10050580 - 29 Apr 2020
Cited by 8 | Viewed by 3119
Abstract
Fabrication of microwave slot array antennas and waveguide bandpass and notch filters using 3D printing has significant advantages in terms of speed and cost even for parts with high mechanical complexity. One disadvantage of Stereolithography (SLA) 3D printed, copper plated microwave components is [...] Read more.
Fabrication of microwave slot array antennas and waveguide bandpass and notch filters using 3D printing has significant advantages in terms of speed and cost even for parts with high mechanical complexity. One disadvantage of Stereolithography (SLA) 3D printed, copper plated microwave components is that some SLA resins have a high Coefficient of Thermal Expansion (CTE), quoted in micrometers per meter per degree or 10−6 per degree. Compared to typically used metals such as aluminum (CTE 24 × 10−6·K−1) and copper (CTE 17 × 10−6·K−1), SLA resin can have CTE above 100 × 10−6·K−1. Resonant structures experience significant frequency drift with temperature changes on the order of 10–50 °C. The issue of 3D printed microwave structures changing frequency characteristics significantly with temperature shift has not been addressed or reviewed in current literature. We measured and simulated the effect of temperature change on a slot array, cavity notch filters, and post loaded waveguide bandpass filters. We tested several types of SLA resin, different plating techniques, and also Direct Metal Laser Sintering (DMLS) and Binder Infusion metal 3D printing. Performance as a function of temperature is presented for these alternatives. Full article
(This article belongs to the Special Issue Metal Additive Manufacturing – State of the Art 2020)
►▼ Show Figures

Figure 1

8 pages, 2326 KiB  
Article
Mechanical Properties of High Strength Aluminum Alloy EN AW-7075 Additively Manufactured by Directed Energy Deposition
by Anika Langebeck, Annika Bohlen, Rüdiger Rentsch and Frank Vollertsen
Metals 2020, 10(5), 579; https://doi.org/10.3390/met10050579 - 29 Apr 2020
Cited by 24 | Viewed by 4045
Abstract
A manifold variety of additive manufacturing techniques has a significant positive impact on many industry sectors. Large components are often manufactured via directed energy deposition (DED) instead of using powder bed fusion processes (PBF). The advantages of the DED process are a high [...] Read more.
A manifold variety of additive manufacturing techniques has a significant positive impact on many industry sectors. Large components are often manufactured via directed energy deposition (DED) instead of using powder bed fusion processes (PBF). The advantages of the DED process are a high build-up rate with values up to 300 cm3/h and a nearly limitless build-up volume. In combination with the lightweight material aluminum it is possible to manufacture large lightweight components with geometries adapted to customer requirements in small batches. This contributes the pursuit of higher efficiency of machines through lightweight materials as well as lightweight design. A low-defect additive manufacturing of high strength aluminum EN AW-7075 powder via DED is an important challenge. The laser power has a significant influence on the remaining porosity. By increasing the laser power from 2 kW to 4 kW the porosity in single welding tracks can be lowered from 2.1% to only (0.09 ± 0.07)% (n = 3). However, when manufacturing larger specimens; the remaining porosity is higher than in single tracks; which can be attributed to the oxide skin on the preceding welding tracks. Further investigations regarding the mechanical properties were carried out. In tensile tests an ultimate tensile strength of (222 ± 17) MPa (n = 6) was measured. The DED processed EN AW-7075 shows comparable mechanical properties to PBF processed EN AW-7075. Full article
(This article belongs to the Special Issue Metal Additive Manufacturing – State of the Art 2020)
►▼ Show Figures

Figure 1

15 pages, 27186 KiB  
Article
Fabrication of Single Crystals through a µ-Helix Grain Selection Process during Electron Beam Metal Additive Manufacturing
by Martin R. Gotterbarm, Alexander M. Rausch and Carolin Körner
Metals 2020, 10(3), 313; https://doi.org/10.3390/met10030313 - 28 Feb 2020
Cited by 43 | Viewed by 7341
Abstract
Selective Electron Beam Melting (SEBM) is a powder bed-based additive manufacturing process for metals. As the electron beam can be moved inertia-free by electromagnetic lenses, the solidification conditions can be deliberately adjusted within the process. This enables control over the local solidification conditions. [...] Read more.
Selective Electron Beam Melting (SEBM) is a powder bed-based additive manufacturing process for metals. As the electron beam can be moved inertia-free by electromagnetic lenses, the solidification conditions can be deliberately adjusted within the process. This enables control over the local solidification conditions. SEBM typically leads to columnar grain structures. Based on numerical simulation, we demonstrated how technical single crystals develop in IN718 by forcing the temperature gradient along a µ-Helix. The slope of the µ-Helix, i.e., the deviation of the thermal gradient from the build direction, determined the effectiveness of grain selection right up to single crystals. Full article
(This article belongs to the Special Issue Metal Additive Manufacturing – State of the Art 2020)
►▼ Show Figures

Figure 1

22 pages, 7032 KiB  
Article
Animal Origin Bioactive Hydroxyapatite Thin Films Synthesized by RF-Magnetron Sputtering on 3D Printed Cranial Implants
by Diana Chioibasu, Liviu Duta, Gianina Popescu-Pelin, Nicoleta Popa, Nichita Milodin, Stefana Iosub, Liliana Marinela Balescu, Aurelian Catalin Galca, Adrian Claudiu Popa, Faik N. Oktar, George E. Stan and Andrei C. Popescu
Metals 2019, 9(12), 1332; https://doi.org/10.3390/met9121332 - 10 Dec 2019
Cited by 17 | Viewed by 3974
Abstract
Ti6Al4V cranial prostheses in the form of patterned meshes were 3D printed by selective laser melting in an argon environment; using a CO2 laser source and micron-sized Ti6Al4V powder as the starting material. The size and shape of prostheses were chosen based [...] Read more.
Ti6Al4V cranial prostheses in the form of patterned meshes were 3D printed by selective laser melting in an argon environment; using a CO2 laser source and micron-sized Ti6Al4V powder as the starting material. The size and shape of prostheses were chosen based on actual computer tomography images of patient skull fractures supplied in the framework of a collaboration with a neurosurgery clinic. After optimizations of scanning speed and laser parameters, the printed material was defect-free (as shown by metallographic analyses) and chemically homogeneous, without elemental segregation or depletion. The prostheses were coated by radio-frequency magnetron sputtering (RF-MS) with a bioactive thin layer of hydroxyapatite using a bioceramic powder derived from biogenic resources (Bio-HA). Initially amorphous, the films were converted to fully-crystalline form by applying a post-deposition thermal-treatment at 500 °C/1 h in air. The X-ray diffraction structural investigations indicated the phase purity of the deposited films composed solely of a hexagonal hydroxyapatite-like compound. On the other hand, the Fourier transform infrared spectroscopic investigations revealed that the biological carbonatation of the bone mineral phase was well-replicated in the case of crystallized Bio-HA RF-MS implant coatings. The in vitro acellular assays, performed in both the fully inorganic Kokubo’s simulated body fluid and the biomimetic organic–inorganic McCoy’s 5A cell culture medium up to 21 days, emphasized both the good resistance to degradation and the biomineralization capacity of the films. Further in vitro tests conducted in SaOs-2 osteoblast-like cells showed a positive proliferation rate on the Bio-HA RF-MS coating along with a good adhesion developed on the biomaterial surface by elongated membrane protrusions. Full article
(This article belongs to the Special Issue Metal Additive Manufacturing – State of the Art 2020)
►▼ Show Figures

Graphical abstract

14 pages, 5055 KiB  
Article
Evaluation of Support Structure Removability for Additively Manufactured Ti6Al4V Overhangs via Electron Beam Melting
by Wadea Ameen, Muneer Khan Mohammed and Abdulrahman Al-Ahmari
Metals 2019, 9(11), 1211; https://doi.org/10.3390/met9111211 - 11 Nov 2019
Cited by 10 | Viewed by 3081
Abstract
The addition of support structures is essential for the successful fabrication of overhang structures through additive manufacturing (AM). The support structures protect the overhang portion from distortions. They are fabricated with the functional parts and are removed later after the fabrication of the [...] Read more.
The addition of support structures is essential for the successful fabrication of overhang structures through additive manufacturing (AM). The support structures protect the overhang portion from distortions. They are fabricated with the functional parts and are removed later after the fabrication of the AM part. While structures bearing insufficient support result in defective overhangs, structures with excessive support result in higher material consumption, time and higher post-processing costs. The objective of this study is to investigate the effects of design and process parameters of support structures on support removability during the electron beam melting (EBM)-based additive manufacturing of the Ti6Al4V overhang part. The support design parameters include tooth parameters, no support offset, fragmentation parameters and perforation parameters. The EBM process parameters consist of beam current, beam scan speed and beam focus offset. The results show that both support design and process parameters have a significant effect on support removability. In addition, with the appropriate selection of design and process parameters, it is possible to significantly reduce the support removal time and protect the surface quality of the part. Full article
(This article belongs to the Special Issue Metal Additive Manufacturing – State of the Art 2020)
►▼ Show Figures

Figure 1

Review

Jump to: Editorial, Research

45 pages, 15850 KiB  
Review
Application of Laser-Based Powder Bed Fusion for Direct Metal Tooling
by Nader Asnafi
Metals 2021, 11(3), 458; https://doi.org/10.3390/met11030458 - 10 Mar 2021
Cited by 14 | Viewed by 4921
Abstract
The journey of production tools in cold working, hot working, and injection molding from rapid tooling to additive manufacturing (AM) by laser-based powder bed fusion (L-PBF) is described. The current machines and their configurations, tool steel powder materials and their properties, and the [...] Read more.
The journey of production tools in cold working, hot working, and injection molding from rapid tooling to additive manufacturing (AM) by laser-based powder bed fusion (L-PBF) is described. The current machines and their configurations, tool steel powder materials and their properties, and the L-PBF process parameters for these materials are specified. Examples of production tools designed for and made by L-PBF are described. Efficient design, i.e., high tooling efficiency and performance in operation, should be the primary target in tool design. Topology and lattice structure optimization provide additional benefits. Using efficient design, L-PBF exhibits the greatest potential for tooling in hot working and injection molding. L-PBF yields high tooling costs, but competitive total costs in hot working and injection molding. Larger object sizes that can be made by L-PBF, a larger number of powder metals that are designed for different tooling applications, lower feedstock and L-PBF processing costs, further L-PBF productivity improvement, improved surface roughness through L-PBF, and secured quality are some of the targets for the research and development in the future. A system view, e.g., plants with a high degree of automation and eventually with cyber-physically controlled smart L-PBF inclusive manufacturing systems, is also of great significance. Full article
(This article belongs to the Special Issue Metal Additive Manufacturing – State of the Art 2020)
►▼ Show Figures

Figure 1

24 pages, 7064 KiB  
Review
A Review of Heat Treatments on Improving the Quality and Residual Stresses of the Ti–6Al–4V Parts Produced by Additive Manufacturing
by Óscar Teixeira, Francisco J. G. Silva, Luís P. Ferreira and Eleonora Atzeni
Metals 2020, 10(8), 1006; https://doi.org/10.3390/met10081006 - 27 Jul 2020
Cited by 65 | Viewed by 8641
Abstract
Additive manufacturing (AM) can be seen as a disruptive process that builds complex components layer upon layer. Two of its distinct technologies are Selective Laser Melting (SLM) and Electron Beam Melting (EBM), which are powder bed fusion processes that create metallic parts with [...] Read more.
Additive manufacturing (AM) can be seen as a disruptive process that builds complex components layer upon layer. Two of its distinct technologies are Selective Laser Melting (SLM) and Electron Beam Melting (EBM), which are powder bed fusion processes that create metallic parts with the aid of a beam source. One of the most studied and manufactured superalloys in metal AM is the Ti–6Al–4V, which can be applied in the aerospace field due to its low density and high melting point, and in the biomedical area owing to its high corrosion resistance and excellent biocompatibility when in contact with tissues or bones of the human body. The research novelty of this work is the aggregation of all kinds of data from the last 20 years of investigation about Ti–6Al–4V parts manufactured via SLM and EBM, namely information related to residual stresses (RS), as well as the influence played by different heat treatments in reducing porosity and increasing mechanical properties. Throughout the report, it can be seen that the expected microstructure of the Ti–6Al–4V alloy is different in both manufacturing processes, mainly due to the distinct cooling rates. However, heat treatments can modify the microstructure, reduce RS, and increase the ductility, fatigue life, and hardness of the components. Furthermore, distinct post-treatments can induce compressive RS on the part’s surface, consequently enhancing the fatigue life. Full article
(This article belongs to the Special Issue Metal Additive Manufacturing – State of the Art 2020)
►▼ Show Figures

Figure 1

Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
 
Displaying articles 1-12
Back to TopTop