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Metals
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Additive Manufacturing Research and Applications
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Additive Manufacturing Research and Applications

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

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 59211

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

Special Issue Editor

Prof. Dr. Atila Ertas

E-Mail Website
Guest Editor
Department of Mechanical Engineering, Texas Tech University, Lubbock, TX 79409, USA
Interests: test method development; galling; transdisciplinary complex system design; 3D printing technology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Additive Manufacturing (AM) has gone through to a certain extent of a revolution over the last decade and now it has evolved into a viable industrial manufacturing solution—creating complex geometries unachievable with traditional manufacturing methods. However, further research required to overcome many challenges additive manufacturing faces today. We welcome you to this special issue of “Additive Manufacturing Research and Applications” to submit papers in the following general research areas of additive manufacturing: powder manufacturing technologies in 3D printing, pre- and post-processing technologies and approaches, AM processes and optimizations, inspection processes and quality evaluation, new materials for 3D printing, design and simulation in AM (topology optimization, microstructure design, new AM machine design and development etc.), and any other interesting research topics regarding 3D printing (additive manufacturing).

Prof. Dr. Atila Ertas
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

  • Additive manufacturing
  • 3D printing
  • Detecting voids in a material
  • Powder-Based 3D Printing
  • Post processing

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Published Papers (19 papers)

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Editorial

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2 pages, 159 KiB  
Editorial
Additive Manufacturing Research and Applications
by Atila Ertas and Adam Stroud
Metals 2022, 12(4), 634; https://0-doi-org.brum.beds.ac.uk/10.3390/met12040634 - 07 Apr 2022
Cited by 2 | Viewed by 1351
Abstract
Additive Manufacturing (AM) has undergone somewhat of a revolution over the last decade and it has now evolved into a viable industrial manufacturing solution, able to create complex geometries which are unachievable with traditional manufacturing methods [...] Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)

Research

Jump to: Editorial, Review

18 pages, 5129 KiB  
Article
Experimental Investigation of Pressure Drop Performance of Smooth and Dimpled Single Plate-Fin Heat Exchangers
by Kanishk Rauthan, Ferdinando Guzzomi, Ana Vafadar, Kevin Hayward and Aakash Hurry
Metals 2021, 11(11), 1757; https://0-doi-org.brum.beds.ac.uk/10.3390/met11111757 - 01 Nov 2021
Cited by 6 | Viewed by 1863
Abstract
Passive heat exchangers (HXs) form an inseparable part of the manufacturing industry as they provide high-efficiency cooling at minimal overhead costs. Along with the aspects of high thermal cooling, it is essential to monitor pressure loss while using plate-fin HXs because pressure loss [...] Read more.
Passive heat exchangers (HXs) form an inseparable part of the manufacturing industry as they provide high-efficiency cooling at minimal overhead costs. Along with the aspects of high thermal cooling, it is essential to monitor pressure loss while using plate-fin HXs because pressure loss can introduce additional power costs to a system. In this paper, an experimental study was conducted to look at the effects of dimples on the pressure drop characteristics of single plate-fin heat exchangers. To enable this, different configurations of National Advisory Committee for Aeronautics (NACA) fins with smooth surfaces and 2 mm-diameter dimples, 4 mm-diameter dimples and 6 mm-diameter dimples were designed and 3D printed using fused deposition modelling (FDM) of ABS plastic. The depth to diameter ratio for these dimples was kept constant at 0.3 with varied diameters and depths. These were then tested using a subsonic wind tunnel comprised of inlet and outlet pressure taps as well as a hot wire velocimeter. Measurements were taken for pressure differences as well as average velocity. These were then used to calculate friction factor values and to compare the smooth fin to the dimpled fins in relation to their relative pressure drop performance. It was observed that for lower velocities the 4 mm dimples provided minimum pressure drop, with a difference of 58% when compared to smooth fins. At higher velocities, 6 mm dimples increased the pressure drop by approximately 34% when compared to smooth fins. It can also be concluded from the observed data in this study that shallower dimples produce lower pressure drops compared to deeper dimples when the depth to diameter ratio is kept constant. Accordingly, deeper dimples are more effective in providing drag reduction at lower velocities, whereas shallower dimples are more effective for drag reduction at higher velocities. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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17 pages, 8163 KiB  
Article
Comparative Study on Microstructure and Corrosion Resistance of Al-Si Alloy Cast from Sand Mold and Binder Jetting Mold
by María Ángeles Castro-Sastre, Cristina García-Cabezón, Ana Isabel Fernández-Abia, Fernando Martín-Pedrosa and Joaquín Barreiro
Metals 2021, 11(9), 1421; https://0-doi-org.brum.beds.ac.uk/10.3390/met11091421 - 08 Sep 2021
Cited by 10 | Viewed by 2378
Abstract
This investigation is focused on the corrosion evaluation of an as-cast Al-Si alloy, obtained by two different casting methods: traditional sand casting and three-printing casting, using a binder jetted mold. The experimental results are discussed in terms of chemical composition, microstructure, hardness, and [...] Read more.
This investigation is focused on the corrosion evaluation of an as-cast Al-Si alloy, obtained by two different casting methods: traditional sand casting and three-printing casting, using a binder jetted mold. The experimental results are discussed in terms of chemical composition, microstructure, hardness, and corrosion behavior of two different casting parts. The microstructure and composition of the sample before and after the corrosion tests was analyzed using light microscopy (OM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (DRX). The corrosion of the two processed castings was analyzed using anodic polarization (PA) test and electrochemical impedance spectroscopy (EIS) in an aerated solution of 3.5% by weight NaCl, similar to the seawater environment. After the corrosion process, the samples were analyzed by inductively coupled plasma/optical emission spectrometry (ICP/OES); the composition was used to determine the chloride solution after immersion times. The sample processed by binder jetting mold showed higher corrosion resistance with nobler potentials, lower corrosion densities, higher polarization resistance, and more stable passive layers than the sample processed by sand casting. This improvement of corrosion resistance could be related to the presence of coarse silicon particles, which decrease of cathodic/anodic ratio and the number of micro-galvanic couples, and the lower amount of intermetallic β Al-Fe-Si phase observed in cast alloy solidified in binder jetting mold. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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16 pages, 5456 KiB  
Article
Deposition of Nickel-Based Superalloy Claddings on Low Alloy Structural Steel by Direct Laser Deposition
by André Alves Ferreira, Rui Loureiro Amaral, Pedro Correia Romio, João Manuel Cruz, Ana Rosanete Reis and Manuel Fernando Vieira
Metals 2021, 11(8), 1326; https://0-doi-org.brum.beds.ac.uk/10.3390/met11081326 - 22 Aug 2021
Cited by 15 | Viewed by 2647
Abstract
In this study, direct laser deposition (DLD) of nickel-based superalloy powders (Inconel 625) on structural steel (42CrMo4) was analysed. Cladding layers were produced by varying the main processing conditions: laser power, scanning speed, feed rate, and preheating. The processing window was established based [...] Read more.
In this study, direct laser deposition (DLD) of nickel-based superalloy powders (Inconel 625) on structural steel (42CrMo4) was analysed. Cladding layers were produced by varying the main processing conditions: laser power, scanning speed, feed rate, and preheating. The processing window was established based on conditions that assured deposited layers without significant structural defects and a dilution between 15 and 30%. Scanning electron microscopy, energy dispersive spectroscopy, and electron backscatter diffraction were performed for microstructural characterisation. The Vickers hardness test was used to analyse the mechanical response of the optimised cladding layers. The results highlight the influence of preheating on the microstructure and mechanical responses, particularly in the heat-affected zone. Substrate preheating to 300 °C has a strong effect on the cladding/substrate interface region, affecting the microstructure and the hardness distribution. Preheating also reduced the formation of the deleterious Laves phase in the cladding and altered the martensite microstructure in the heat-affected zone, with a substantial decrease in hardness. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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13 pages, 7428 KiB  
Article
Fatigue Assessment of Selective Laser Melted Ti-6Al-4V: Influence of Speed Manufacturing and Porosity
by Unai Segurajauregi, Adrián Álvarez-Vázquez, Miguel Muñiz-Calvente, Íker Urresti and Haydee Naveiras
Metals 2021, 11(7), 1022; https://0-doi-org.brum.beds.ac.uk/10.3390/met11071022 - 25 Jun 2021
Cited by 7 | Viewed by 1859
Abstract
Additive Manufacturing represents a promising technology as an alternative to the conventional manufacturing process, with rapid and economic product development, as well as a significant weight reduction and a freeform design. Although the mechanical properties of additively manufactured metals, such as the Ti-6Al-4V [...] Read more.
Additive Manufacturing represents a promising technology as an alternative to the conventional manufacturing process, with rapid and economic product development, as well as a significant weight reduction and a freeform design. Although the mechanical properties of additively manufactured metals, such as the Ti-6Al-4V alloy, are well-established, a complete understanding of the fatigue performance is still a pending aspiration due to its inherent stochastic complexity and the influence of several manufacturing factors. This paper presents a study of the influence of speed manufacturing and porosity in the fatigue behaviour of a Ti-6Al-4V alloy. To this aim, a numerical simulation of the expected porosity at different laser velocities is performed, together with a simulation of the residual stresses. These numerical results are compared with experimental measurements of residual stresses and a qualitative analysis of the porosities. Then, fatigue strength is experimentally obtained for two different laser speeds and fitted by a probabilistic model. As a result, the probabilistic S–N fields for different laser velocities are found to be similar, with scatter bands nearly coincident, drawing the conclusion that this effect is negligible in comparison with other concurrent ones, such as roughness or surface defects from manufacturing conditions, promoting crack initiation and premature fatigue failure. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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12 pages, 1746 KiB  
Article
In Vitro Physical-Chemical Behaviour Assessment of 3D-Printed CoCrMo Alloy for Orthopaedic Implants
by Radu Mirea, Iuliana Manuela Biris, Laurentiu Constantin Ceatra, Razvan Ene, Alexandru Paraschiv, Andrei Tiberiu Cucuruz, Gabriela Sbarcea, Elisa Popescu and Teodor Badea
Metals 2021, 11(6), 857; https://0-doi-org.brum.beds.ac.uk/10.3390/met11060857 - 24 May 2021
Cited by 6 | Viewed by 1751
Abstract
In this study, a CoCrMo-based metallic alloy was manufactured using a 3D-printing method with metallic powder and a laser-based 3D printer. The obtained material was immersed in a simulated body fluid (SBF) similar to blood plasma and kept 2 months at 37 °C [...] Read more.
In this study, a CoCrMo-based metallic alloy was manufactured using a 3D-printing method with metallic powder and a laser-based 3D printer. The obtained material was immersed in a simulated body fluid (SBF) similar to blood plasma and kept 2 months at 37 °C and in relative motion against the SBF in order to mimic the real motion of body fluids against an implant. At determined time intervals (24, 72, 168, 336, and 1344 h), both the metallic sample and SBF were characterized from a physical-chemical point of view in order to assess the alloy’s behaviour in the SBF. Firstly, the CoCrMo based metallic sample was characterized by scanning electron microscopy (SEM) for assessing surface corrosion and X-ray diffraction (XRD) for determining if and/or what kind of spontaneous protective layer was formed on the surface; secondly, the SBF was characterized by pH, electrical conductivity (EC), and inductively coupled plasma mass spectroscopy (ICP-MS) for assessing the metal ion release. We determined that a 3D-printed CoCrMo alloy does not represent a potential biological hazard in terms of the concentration of metal ion releases, since it forms, in a relatively short period of time, a protective CoCr layer on its exposed surface. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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8 pages, 2998 KiB  
Article
3D-Printed Connector for Revision Limb Salvage Surgery in Long Bones Previously Using Customized Implants
by Jong-Woong Park, Hyun-Guy Kang, June-Hyuk Kim and Han-Soo Kim
Metals 2021, 11(5), 707; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050707 - 26 Apr 2021
Cited by 5 | Viewed by 3837
Abstract
In orthopedic oncology, revisional surgery due to mechanical failure or local recurrence is not uncommon following limb salvage surgery using an endoprosthesis. However, due to the lack of clinical experience in limb salvage surgery using 3D-printed custom-made implants, there have been no reports [...] Read more.
In orthopedic oncology, revisional surgery due to mechanical failure or local recurrence is not uncommon following limb salvage surgery using an endoprosthesis. However, due to the lack of clinical experience in limb salvage surgery using 3D-printed custom-made implants, there have been no reports of revision limb salvage surgery using a 3D-printed implant. Herein, we present two cases of representative revision limb salvage surgeries that utilized another 3D-printed custom-made implant while retaining the previous 3D-printed custom-made implant. A 3D-printed connector implant was used to connect the previous 3D-printed implant to the proximal ulna of a 40-year-old man and to the femur of a 69-year-old woman. The connector bodies for the two junctions of the previous implant and the remaining host bone were designed for the most functional position or angle by twisting or tilting. Using the previous 3D-printed implant as a taper, the 3D-printed connector was used to encase the outside of the previous implant. The gap between the previous implant and the new one was subsequently filled with bone cement. For both the upper and lower extremities, the 3D-printed connector showed stable reconstruction and excellent functional outcomes (Musculoskeletal Tumor Society scores of 87% and 100%, respectively) in the short-term follow-up. To retain the previous 3D-printed implant during revision limb salvage surgery, an additional 3D-printed implant may be a feasible surgical option. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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14 pages, 5465 KiB  
Article
Fabrication of a TiC-Ti Matrix Composite Coating Using Ultrasonic Vibration-Assisted Laser Directed Energy Deposition: The Effects of Ultrasonic Vibration and TiC Content
by Yunze Li, Dongzhe Zhang, Hui Wang and Weilong Cong
Metals 2021, 11(5), 693; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050693 - 23 Apr 2021
Cited by 10 | Viewed by 2312
Abstract
Titanium and its alloys exhibit superior properties of high corrosion resistance, an excellent strength to weight ratio and outstanding stiffness among other things. However, their relatively low hardness and wear resistance limit their service life in high-performance applications of structure parts, gears and [...] Read more.
Titanium and its alloys exhibit superior properties of high corrosion resistance, an excellent strength to weight ratio and outstanding stiffness among other things. However, their relatively low hardness and wear resistance limit their service life in high-performance applications of structure parts, gears and bearings, for example. The fabrication of a ceramic reinforced titanium matrix composite (TMC) coating could be one of the solutions to enhance the microhardness and wear resistance. Titanium carbide (TiC) is a preferable candidate due to the advantages of self-lubrication, low cost and a similar density and thermal expansion coefficient with titanium. The fabrication of TiC-TMC coatings onto titanium using a laser directed energy deposition (LDED) process has been conducted. The problems of TiC aggregation, low bonding quality and the generation of fabrication defects still exist. Considering ultrasonic vibration could generate acoustic steaming and transient cavitation actions in melted materials, which could homogenize the distribution of reinforcement materials and promote the dissolution of TiC into liquid titanium. In this study, for the first time, we investigate the ultrasonic vibration-assisted LDED of TiC-TMC coatings. The effects of ultrasonic vibration and reinforcement content on the phase compositions, reinforcement aggregation, bonding quality, fabrication defects and mechanical properties (including microhardness and wear resistance) of LDED deposited TiC-TMC coatings have been investigated. With the assistance of ultrasonic vibration, the aggregation of TiC was reduced, the porosity was decreased, the defects in the bonding interface were reduced and the mechanical properties including microhardness and wear resistance were increased. However, the excessive TiC content could significantly increase the TiC aggregation and manufacturing defects, resulting in the reduction of the mechanical properties. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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16 pages, 5299 KiB  
Article
Model for the Prediction of Deformations in the Manufacture of Thin-Walled Parts by Wire Arc Additive Manufacturing Technology
by Mikel Casuso, Fernando Veiga, Alfredo Suárez, Trunal Bhujangrao, Eider Aldalur, Teresa Artaza, Jaime Amondarain and Aitzol Lamikiz
Metals 2021, 11(5), 678; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050678 - 21 Apr 2021
Cited by 26 | Viewed by 3211
Abstract
Gas Metal Arc Welding (GMAW) is a manufacturing technology included within the different Wire Arc Additive Manufacturing alternatives. These technologies have been generating great attention among scientists in recent decades. Its main qualities that make it highly productive with a large use of [...] Read more.
Gas Metal Arc Welding (GMAW) is a manufacturing technology included within the different Wire Arc Additive Manufacturing alternatives. These technologies have been generating great attention among scientists in recent decades. Its main qualities that make it highly productive with a large use of material with relatively inexpensive machine solutions make it a very advantageous technology. This paper covers the application of this technology for the manufacture of thin-walled parts. A finite element model is presented for estimating the deformations in this type of parts. This paper presents a simulation model that predicts temperatures with less than 5% error and deformations of the final part that, although quantitatively has errors of 20%, qualitatively allows to know the deformation modes of the part. Knowing the part areas subject to greater deformation may allow the future adaptation of deposition strategies or redesigns for their adaptation. These models are very useful both at a scientific and industrial level since when we find ourselves with a technology oriented to Near Net Shape (NNS) manufacturing where deformations are critical for obtaining the final part in a quality regime. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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19 pages, 59517 KiB  
Article
Feasibility Study of the Cranial Implant Fabricated without Supports in Electron Beam Melting
by Khaja Moiduddin, Syed Hammad Mian, Wadea Ameen, Hisham Alkhalefah and Abdul Sayeed
Metals 2021, 11(3), 496; https://0-doi-org.brum.beds.ac.uk/10.3390/met11030496 - 17 Mar 2021
Cited by 5 | Viewed by 2236
Abstract
Additive manufacturing (AM), particularly electron beam melting (EBM), is becoming increasingly common in the medical industry because of its remarkable benefits. The application of personalized titanium alloy implants produced using EBM has received considerable attention in recent times due to their simplicity and [...] Read more.
Additive manufacturing (AM), particularly electron beam melting (EBM), is becoming increasingly common in the medical industry because of its remarkable benefits. The application of personalized titanium alloy implants produced using EBM has received considerable attention in recent times due to their simplicity and efficacy. However, these tailored implants are not cost-effective, placing a tremendous strain on the patient. The use of additional materials as support during the manufacturing process is one of the key causes of its high cost. A lot of research has been done to lessen the use of supports through various types of support designs. There is indeed a noticeable paucity of studies in the literature that have examined customized implants produced without or minimal supports. This research, therefore, reports on the investigation of cranial implants fabricated with and without supports. The two personalized implants are evaluated in terms of their cost, fabrication time, and accuracy. The study showed impressive results for cranial implants manufactured without supports that cost 39% less than the implants with supports. Similarly, the implant’s (without supports) build time was 18% less than its equivalent with supports. The two implants also demonstrated similar fitting accuracy with 0.2613 mm error in the instance of implant built without supports and 0.2544 mm for the implant with supports. The results indicate that cranial implants can be produced without EBM supports, which can minimize both production time and cost substantially. However, the manufacture of other complex implants without supports needs further study. The future study also requires a detailed review of the mechanical and structural characteristics of cranial implants built without supports. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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15 pages, 6010 KiB  
Article
The Influence of Particle Shape, Powder Flowability, and Powder Layer Density on Part Density in Laser Powder Bed Fusion
by Lukas Haferkamp, Livia Haudenschild, Adriaan Spierings, Konrad Wegener, Kirstin Riener, Stefan Ziegelmeier and Gerhard J. Leichtfried
Metals 2021, 11(3), 418; https://0-doi-org.brum.beds.ac.uk/10.3390/met11030418 - 04 Mar 2021
Cited by 54 | Viewed by 5960
Abstract
The particle shape influences the part properties in laser powder bed fusion, and powder flowability and powder layer density (PLD) are considered the link between the powder and part properties. Therefore, this study investigates the relationship between these properties and their influence on [...] Read more.
The particle shape influences the part properties in laser powder bed fusion, and powder flowability and powder layer density (PLD) are considered the link between the powder and part properties. Therefore, this study investigates the relationship between these properties and their influence on final part density for six 1.4404 (316L) powders and eight AlSi10Mg powders. The results show a correlation of the powder properties with a Pearson correlation coefficient (PCC) of −0.89 for the PLD and the Hausner ratio, a PCC of −0.67 for the Hausner ratio and circularity, and a PCC of 0.72 for circularity and PLD. Furthermore, the results show that beyond a threshold, improvement of circularity, PLD, or Hausner ratio have no positive influence on the final part density. While the water-atomized, least-spherical powder yielded parts with high porosity, no improvement of part density was achieved by feedstock with higher circularities than gas-atomized powder. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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24 pages, 6675 KiB  
Article
Innovative Methodology for the Identification of the Most Suitable Additive Technology Based on Product Characteristics
by Antonio Del Prete and Teresa Primo
Metals 2021, 11(3), 409; https://0-doi-org.brum.beds.ac.uk/10.3390/met11030409 - 02 Mar 2021
Cited by 5 | Viewed by 1720
Abstract
This paper reports the study and development case of an innovative application of the Cloud Manufacturing paradigm. Based on the definition of an appropriate web-based application, the infrastructure is able to connect the possible client requests and the relative supply chain product/process development [...] Read more.
This paper reports the study and development case of an innovative application of the Cloud Manufacturing paradigm. Based on the definition of an appropriate web-based application, the infrastructure is able to connect the possible client requests and the relative supply chain product/process development capabilities and then attempt to find the best available solutions. In particular, the main goal of the developed system, called AMSA (Additive Manufacturing Spare parts market Application), is the definition of a common platform to supply different kinds of services that have the following common reference points in the Additive Manufacturing Technologies (DFAM, Design For Additive Manufacturing): product development, prototypes, or small series production and reverse engineering activities to obtain Computer-Aided Design (CAD) models starting from a physical object. The definition of different kinds of services allows satisfying several client needs such as innovative product definition characterized by high performance in terms of stiffness/weight ratio, the possibility of manufacturing small series, such as in the motorsport field, and the possibility of defining CAD models for the obsolete parts for which the geometrical information is missed. The AMSA platform relies on the reconfigurable supply chain that is dynamic, and it depends on the client needs. For example, when the client requires the manufacture of a small series of a component, AMSA allows the technicians to choose the best solutions in terms of delivery time, price, and logistics. Therefore, the suppliers that contribute to the definition of the dynamic supply chain have an important role. For these reasons, the AMSA platform represents an important and innovative tool that is able to link the suppliers to the customers in the best manner in order to obtain services that are characterized by a high-performance level. Therefore, a provisional model has been implemented that allows filtering the technologies according to suitable performance indexes. A specific aspect for which AMSA can be considered unique is related with the given possibility to access Design for Additive Manufacturing Services through the Web in accordance with the possible additive manufacturing technologies. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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19 pages, 6313 KiB  
Article
Deep Learning-Based Ultrasonic Testing to Evaluate the Porosity of Additively Manufactured Parts with Rough Surfaces
by Seong-Hyun Park, Jung-Yean Hong, Taeho Ha, Sungho Choi and Kyung-Young Jhang
Metals 2021, 11(2), 290; https://0-doi-org.brum.beds.ac.uk/10.3390/met11020290 - 08 Feb 2021
Cited by 20 | Viewed by 3246
Abstract
Ultrasonic testing (UT) has been actively studied to evaluate the porosity of additively manufactured parts. Currently, ultrasonic measurements of as-deposited parts with a rough surface remain problematic because the surface lowers the signal-to-noise ratio (SNR) of ultrasonic signals, which degrades the UT performance. [...] Read more.
Ultrasonic testing (UT) has been actively studied to evaluate the porosity of additively manufactured parts. Currently, ultrasonic measurements of as-deposited parts with a rough surface remain problematic because the surface lowers the signal-to-noise ratio (SNR) of ultrasonic signals, which degrades the UT performance. In this study, various deep learning (DL) techniques that can effectively extract the features of defects, even from signals with a low SNR, were applied to UT, and their performance in terms of the porosity evaluation of additively manufactured parts with rough surfaces was investigated. Experimentally, the effects of the processing conditions of additive manufacturing on the resulting porosity were first analyzed using both optical and scanning acoustic microscopy. Second, convolutional neural network (CNN), deep neural network, and multi-layer perceptron models were trained using time-domain ultrasonic signals obtained from additively manufactured specimens with various levels of porosity and surface roughness. The experimental results showed that all the models could evaluate porosity accurately, even that of the as-deposited specimens. In particular, the CNN delivered the best performance at 94.5%. However, conventional UT could not be applied because of the low SNR. The generalization performance when using newly manufactured as-deposited specimens was high at 90%. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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13 pages, 11040 KiB  
Article
Microstructure and Mechanical Properties of Nickel-Based Coatings Fabricated through Laser Additive Manufacturing
by Shaoxiang Qian, Yongkang Zhang, Yibo Dai and Yuhang Guo
Metals 2021, 11(1), 53; https://0-doi-org.brum.beds.ac.uk/10.3390/met11010053 - 29 Dec 2020
Cited by 8 | Viewed by 2319
Abstract
In this study, single-layer and three-layer nickel-based coatings were fabricated on 316L SS by laser additive manufacturing. The phase characterization, microstructure observation, and microhardness analysis of the coatings were carried out by X-ray diffraction (XRD), scanning electron microscope (SEM), and microhardness tester. And [...] Read more.
In this study, single-layer and three-layer nickel-based coatings were fabricated on 316L SS by laser additive manufacturing. The phase characterization, microstructure observation, and microhardness analysis of the coatings were carried out by X-ray diffraction (XRD), scanning electron microscope (SEM), and microhardness tester. And the wear resistance of the coatings was analyzed through dry sliding friction and wear test. The results show that the cross-section microstructure of the three-layer nickel-based coating is different from that of the single-layer one under the influence of heat accumulation; the dendrite structure in the central region of the former is equiaxial dendrite, while that of the latter still remains large columnar dendrites. The existence of solid solution phase γ-(Fe, Ni) and hard phases of Ni17Si3, Cr5B3, Ni3B in the coating significantly improve the wear resistance of the coating, and the microhardness is nearly 2.5 times higher than that of the substrate. However, the average microhardness of multilayer cladding coating is about 48 HV0.2 higher than that of the single-layer cladding coating. In addition, the fine surface structure of the three-layer nickel-based coating improves the wear resistance of the coating, making this coating with the best wear resistance. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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18 pages, 3125 KiB  
Article
Comparison between Virgin and Recycled 316L SS and AlSi10Mg Powders Used for Laser Powder Bed Fusion Additive Manufacturing
by Shahir Mohd Yusuf, Edmund Choo and Nong Gao
Metals 2020, 10(12), 1625; https://0-doi-org.brum.beds.ac.uk/10.3390/met10121625 - 03 Dec 2020
Cited by 24 | Viewed by 4680
Abstract
In this study, the comparison of properties between fresh (virgin) and used (recycled) 316L stainless steel (316L SS) and AlSi10Mg powders for the laser powder bed fusion additive manufacturing (L-PBF AM) process has been investigated in detail. Scanning electron microscopy (SEM), electron-dispersive X-ray [...] Read more.
In this study, the comparison of properties between fresh (virgin) and used (recycled) 316L stainless steel (316L SS) and AlSi10Mg powders for the laser powder bed fusion additive manufacturing (L-PBF AM) process has been investigated in detail. Scanning electron microscopy (SEM), electron-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) techniques are used to determine and evaluate the evolution of morphology, particle size distribution (PSD), circularity, chemical composition, and phase (crystal structure) in the virgin and recycled powders of both materials. The results indicate that both recycled powders increase the average particle sizes and shift the PSD to higher values, compared with their virgin powders. The recycled 316L SS powder particles largely retain their spherical and near-spherical morphologies, whereas more irregularly shaped morphologies are observed for the recycled AlSi10Mg counterpart. The average circularity of recycled 316L SS powder only reduces by ~2%, but decreases ~17% for the recycled AlSi10Mg powder. EDX analysis confirms that both recycled powders retain their alloy-specific chemical compositions, but with increased oxygen content. XRD spectra peak analysis suggests that there are no phase change and no presence of any undesired precipitates in both recycled powders. Based on qualitative comparative analysis between the current results and from various available literature, the reuse of both recycled powders is acceptable up to 30 times, but re-evaluation through physical and chemical characterizations of the powders is advised, if they are to be subjected for further reuse. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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19 pages, 7243 KiB  
Article
Effect of Processing Atmosphere and Secondary Operations on the Mechanical Properties of Additive Manufactured AISI 316L Stainless Steel by Plasma Metal Deposition
by Cristina Arévalo, Enrique Ariza, Eva Maria Pérez-Soriano, Michael Kitzmantel, Erich Neubauer and Isabel Montealegre-Meléndez
Metals 2020, 10(9), 1125; https://0-doi-org.brum.beds.ac.uk/10.3390/met10091125 - 21 Aug 2020
Cited by 4 | Viewed by 2085
Abstract
Plasma metal deposition (PMD) is an interesting additive technique whereby diverse materials can be employed to produce end parts with complex geometries. This study investigates not only the effects of the manufacturing conditions on the final properties of 316L stainless steel specimens by [...] Read more.
Plasma metal deposition (PMD) is an interesting additive technique whereby diverse materials can be employed to produce end parts with complex geometries. This study investigates not only the effects of the manufacturing conditions on the final properties of 316L stainless steel specimens by PMD, but it also affords an opportunity to study how secondary treatments could modify these properties. The tested processing condition was the atmosphere, either air or argon, with the other parameters having previously been optimized. Furthermore, two standard thermal treatments were conducted with the intention of broadening knowledge regarding how these secondary operations could cause changes in the microstructure and properties of 316L parts. To better appreciate and understand the variation of conditions affecting the behavior properties, a thorough characterization of the specimens was carried out. The results indicate that the presence of vermicular ferrite (δ) varied slightly as a consequence of the processing conditions, since it was less prone to appear in specimens manufactured in argon than in air. In this respect, their mechanical properties suffered variations; the higher the ferrite (δ) content, the higher the mechanical properties measured. The degree of influence of the thermal treatment was similar regardless of the processing conditions, which affected the properties based on the heating temperature. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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13 pages, 4704 KiB  
Article
Prediction of Weld Reinforcement Based on Vision Sensing in GMA Additive Manufacturing Process
by Rongwei Yu, Zhuang Zhao, Lianfa Bai and Jing Han
Metals 2020, 10(8), 1041; https://0-doi-org.brum.beds.ac.uk/10.3390/met10081041 - 02 Aug 2020
Cited by 7 | Viewed by 2686
Abstract
In the gas-metal-arc (GMA) additive manufacturing process, the shape of the molten pool, the temperature field of the workpiece and the heat dissipation conditions change with the increase of cladding layers, which can affect the dimensional accuracy of the workpiece; hence, it is [...] Read more.
In the gas-metal-arc (GMA) additive manufacturing process, the shape of the molten pool, the temperature field of the workpiece and the heat dissipation conditions change with the increase of cladding layers, which can affect the dimensional accuracy of the workpiece; hence, it is necessary to monitor the additive manufacturing process online. At present, there is little research about formation-dimension monitoring in the GMA additive manufacturing process; in this paper, weld reinforcement prediction in the GMA additive manufacturing process was conducted, the visual-sensing system for molten pool was established, and a laser locating system was designed to match every frame of the molten pool image with the actual weld location. Extracting the shape and location features of the molten pool as visual features, on the basis of a back-propagation (BP) neural network, we developed the prediction model for weld reinforcement in the GMA additive manufacturing process. Experiment results showed that the model could accurately predict weld reinforcement. By changing the cooling time between adjacent cladding layers, the generalization ability of the prediction model was further verified. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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15 pages, 8154 KiB  
Article
Spreading Process Maps for Powder-Bed Additive Manufacturing Derived from Physics Model-Based Machine Learning
by Prathamesh S. Desai and C. Fred Higgs III
Metals 2019, 9(11), 1176; https://0-doi-org.brum.beds.ac.uk/10.3390/met9111176 - 31 Oct 2019
Cited by 40 | Viewed by 5640
Abstract
The powder bed additive manufacturing (AM) process is comprised of two repetitive steps—spreading of powder and selective fusing or binding the spread layer. The spreading step consists of a rolling and sliding spreader which imposes a shear flow and normal stress on an [...] Read more.
The powder bed additive manufacturing (AM) process is comprised of two repetitive steps—spreading of powder and selective fusing or binding the spread layer. The spreading step consists of a rolling and sliding spreader which imposes a shear flow and normal stress on an AM powder between itself and an additively manufactured substrate. Improper spreading can result in parts with a rough exterior and porous interior. Thus it is necessary to develop predictive capabilities for this spreading step. A rheometry-calibrated model based on the polydispersed discrete element method (DEM) and validated for single layer spreading was applied to study the relationship between spreader speeds and spread layer properties of an industrial grade Ti-6Al-4V powder. The spread layer properties used to quantify spreadability of the AM powder, i.e., the ease with which an AM powder spreads under a set of load conditions, include mass of powder retained in the sampling region after spreading, spread throughput, roughness of the spread layer and porosity of the spread layer. Since the physics-based DEM simulations are computationally expensive, physics model-based machine learning, in the form of a feed forward, back propagation neural network, was employed to interpolate between the highly nonlinear results obtained by running modest numbers of DEM simulations. The minimum accuracy of the trained neural network was 96%. A spreading process map was generated to concisely present the relationship between spreader speeds and spreadability parameters. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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Review

Jump to: Editorial, Research

48 pages, 9757 KiB  
Review
A Review of SLMed Magnesium Alloys: Processing, Properties, Alloying Elements and Postprocessing
by Shuai Liu and Hanjie Guo
Metals 2020, 10(8), 1073; https://0-doi-org.brum.beds.ac.uk/10.3390/met10081073 - 09 Aug 2020
Cited by 30 | Viewed by 5155
Abstract
Selective laser melting (SLM) is an additive manufacturing method with rapid solidification properties, which is conducive to the preparation of alloys with fine microstructures and uniform chemical compositions. Magnesium alloys are lightweight materials that are widely used in the aerospace, biomedical and other [...] Read more.
Selective laser melting (SLM) is an additive manufacturing method with rapid solidification properties, which is conducive to the preparation of alloys with fine microstructures and uniform chemical compositions. Magnesium alloys are lightweight materials that are widely used in the aerospace, biomedical and other fields due to their low density, high specific strength, and good biocompatibility. However, the poor laser formability of magnesium alloy restricts its application. This paper discusses the current research status both related to the theoretical understanding and technology applications. There are problems such as limited processable materials, immature process conditions and metallurgical defects on SLM processing magnesium alloys. Some efforts have been made to solve the above problems, such as adding alloy elements and applying postprocessing. However, the breakthroughs in these two areas are rarely reviewed. Due to the paucity of publications on postprocessing and alloy design of SLMed magnesium alloy powders, we review the current state of research and progress. Moreover, traditional preparation techniques of magnesium alloys are evaluated and related to the SLM process with a view to gaining useful insights, especially with respect to the postprocessing and alloy design of magnesium alloys. The paper also reviews the influence of process parameters on formability, densification and mechanical behavior of magnesium. In addition, the progress of microstructure and metallurgical defects encountered in the SLM processed parts is described. Finally, this article summarizes the research results, and with respect to materials and metallurgy, the new challenges and prospects in the SLM processing of magnesium alloy powders are proposed with respect to alloy design, base material purification, inclusion control and theoretical calculation, and the role of intermetallic compounds. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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