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Special Issue "Perspectives on Additively Manufactured Metallic Materials"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: 31 December 2017

Special Issue Editor

Guest Editor
Prof. Dr. Amir A. Zadpoor

Delft University of Technology (TUDelft) Mekelweg 2, Delft 2628CD, the Netherlands
Website | E-Mail
Interests: biofabrication and additive bio-manufacturing; mechanobiology; surface bio-functionalization; infection prevention and treatment; metamaterials

Special Issue Information

Dear Colleagues,

Recent advances in additive manufacturing (AM) techniques offer many opportunities in terms of design freedom. Complex geometries that could not be easily manufactured using conventional techniques are relatively easy to manufacture using AM. AM of metals has been receiving particular attention, because functional parts in the various industrial sectors can now be fabricated using AM techniques. This Special Issue is, therefore, dedicated to the various areas of research relevant to metal AM. The processing parameters are known to be particularly important in metal AM. The relationship between processing parameters and the resulting microstructure and mechanical properties is one of the most important aspects that need to be studied. Process monitoring and (real-time) adaptation of processing parameters are also of great importance to enable first-time-right AM of metals. Furthermore, the quasi-static and fatigue behavior of AM metallic materials are not yet well understood and will be also covered in this Special Issue. Designer materials, where the microstructure and, thus, mechanical properties of AM materials are (locally) ‘designed’ and achieved through adjustment of processing parameters are also of interest. Finally, AM of new materials, development and improvement of new AM processes and systems, standardization of AM processes and materials, quality control in metal AM, metal powder characterization and standardization, and the other relevant aspects of metal AM are also of interest.

Assoc. Prof. Dr. Amir A. Zadpoor
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 papers will be 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. Materials 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 1500 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

  • Metallic materials;

  • Microstructure-property relationship

  • Designer materials

  • First-time-right additive manufacturing

  • New metal additive manufacturing processes and systems

  • AM of new materials

  • Standardization and quality control in metal additive manufacturing

  • Mechanical behavior of additively manufactured metallic materials including quasi-static mechanical properties, fatigue resistance (crack initiation and propagation), and fracture mechanisms

Published Papers (5 papers)

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Research

Open AccessArticle Three-Dimensional (3D) Printing of Polymer-Metal Hybrid Materials by Fused Deposition Modeling
Materials 2017, 10(10), 1199; doi:10.3390/ma10101199
Received: 31 August 2017 / Revised: 15 October 2017 / Accepted: 16 October 2017 / Published: 19 October 2017
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Abstract
Fused deposition modeling (FDM) is a three-dimensional (3D) printing technology that is usually performed with polymers that are molten in a printer nozzle and placed line by line on the printing bed or the previous layer, respectively. Nowadays, hybrid materials combining polymers with
[...] Read more.
Fused deposition modeling (FDM) is a three-dimensional (3D) printing technology that is usually performed with polymers that are molten in a printer nozzle and placed line by line on the printing bed or the previous layer, respectively. Nowadays, hybrid materials combining polymers with functional materials are also commercially available. Especially combinations of polymers with metal particles result in printed objects with interesting optical and mechanical properties. The mechanical properties of objects printed with two of these metal-polymer blends were compared to common poly (lactide acid) (PLA) printed objects. Tensile tests and bending tests show that hybrid materials mostly containing bronze have significantly reduced mechanical properties. Tensile strengths of the 3D-printed objects were unexpectedly nearly identical with those of the original filaments, indicating sufficient quality of the printing process. Our investigations show that while FDM printing allows for producing objects with mechanical properties similar to the original materials, metal-polymer blends cannot be used for the rapid manufacturing of objects necessitating mechanical strength. Full article
(This article belongs to the Special Issue Perspectives on Additively Manufactured Metallic Materials)
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Open AccessFeature PaperArticle Functionalization of Biomedical Ti6Al4V via In Situ Alloying by Cu during Laser Powder Bed Fusion Manufacturing
Materials 2017, 10(10), 1154; doi:10.3390/ma10101154
Received: 27 August 2017 / Revised: 30 September 2017 / Accepted: 1 October 2017 / Published: 3 October 2017
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Abstract
The modern medical industry successfully utilizes Laser Powder Bed Fusion (LPBF) to manufacture complex custom implants. Ti6Al4V is one of the most commonly used biocompatible alloys. In surgery practice, infection at the bone–implant interface is one of the key reasons for implant failure.
[...] Read more.
The modern medical industry successfully utilizes Laser Powder Bed Fusion (LPBF) to manufacture complex custom implants. Ti6Al4V is one of the most commonly used biocompatible alloys. In surgery practice, infection at the bone–implant interface is one of the key reasons for implant failure. Therefore, advanced implants with biocompatibility and antibacterial properties are required. Modification of Ti alloy with Cu, which in small concentrations is a proven non-toxic antibacterial agent, is an attractive way to manufacture implants with embedded antibacterial functionality. The possibility of achieving alloying in situ, during manufacturing, is a unique option of the LPBF technology. It provides unique opportunities to manufacture customized implant shapes and design new alloys. Nevertheless, optimal process parameters need to be established for the in situ alloyed materials to form dense parts with required mechanical properties. This research is dedicated to an investigation of Ti6Al4V (ELI)-1 at % Cu material, manufactured by LPBF from a mixture of Ti6Al4V (ELI) and pure Cu powders. The effect of process parameters on surface roughness, chemical composition and distribution of Cu was investigated. Chemical homogeneity was discussed in relation to differences in the viscosity and density of molten Cu and Ti6Al4V. Microstructure, mechanical properties, and fracture behavior of as-built 3D samples were analyzed and discussed. Pilot antibacterial functionalization testing of Ti6Al4V (ELI) in situ alloyed with 1 at % Cu showed promising results and notable reduction in the growth of pure cultures of Escherichia coli and Staphylococcus aureus. Full article
(This article belongs to the Special Issue Perspectives on Additively Manufactured Metallic Materials)
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Open AccessArticle On the Anisotropic Mechanical Properties of Selective Laser-Melted Stainless Steel
Materials 2017, 10(10), 1136; doi:10.3390/ma10101136
Received: 18 August 2017 / Revised: 22 September 2017 / Accepted: 24 September 2017 / Published: 26 September 2017
Cited by 1 | PDF Full-text (6018 KB) | HTML Full-text | XML Full-text
Abstract
The thorough description of the peculiarities of additively manufactured (AM) structures represents a current challenge for aspiring freeform fabrication methods, such as selective laser melting (SLM). These methods have an immense advantage in the fast fabrication (no special tooling or moulds required) of
[...] Read more.
The thorough description of the peculiarities of additively manufactured (AM) structures represents a current challenge for aspiring freeform fabrication methods, such as selective laser melting (SLM). These methods have an immense advantage in the fast fabrication (no special tooling or moulds required) of components, geometrical flexibility in their design, and efficiency when only small quantities are required. However, designs demand precise knowledge of the material properties, which in the case of additively manufactured structures are anisotropic and, under certain circumstances, inhomogeneous in nature. Furthermore, these characteristics are highly dependent on the fabrication settings. In this study, the anisotropic tensile properties of selective laser-melted stainless steel (1.4404, 316L) are investigated: the Young’s modulus ranged from 148 to 227 GPa, the ultimate tensile strength from 512 to 699 MPa, and the breaking elongation ranged, respectively, from 12% to 43%. The results were compared to related studies in order to classify the influence of the fabrication settings. Furthermore, the influence of the chosen raw material was addressed by comparing deviations on the directional dependencies reasoned from differing microstructural developments during manufacture. Stainless steel was found to possess its maximum strength at a 45° layer versus loading offset, which is precisely where AlSi10Mg was previously reported to be at its weakest. Full article
(This article belongs to the Special Issue Perspectives on Additively Manufactured Metallic Materials)
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Open AccessFeature PaperArticle Effects of Processing Parameters on Surface Roughness of Additive Manufactured Ti-6Al-4V via Electron Beam Melting
Materials 2017, 10(10), 1121; doi:10.3390/ma10101121
Received: 31 August 2017 / Revised: 18 September 2017 / Accepted: 20 September 2017 / Published: 22 September 2017
Cited by 1 | PDF Full-text (7844 KB) | HTML Full-text | XML Full-text
Abstract
As one of the powder bed fusion additive manufacturing technologies, electron beam melting (EBM) is gaining more and more attention due to its near-net-shape production capacity with low residual stress and good mechanical properties. These characteristics also allow EBM built parts to be
[...] Read more.
As one of the powder bed fusion additive manufacturing technologies, electron beam melting (EBM) is gaining more and more attention due to its near-net-shape production capacity with low residual stress and good mechanical properties. These characteristics also allow EBM built parts to be used as produced without post-processing. However, the as-built rough surface introduces a detrimental influence on the mechanical properties of metallic alloys. Thereafter, understanding the effects of processing parameters on the part’s surface roughness, in turn, becomes critical. This paper has focused on varying the processing parameters of two types of contouring scanning strategies namely, multispot and non-multispot, in EBM. The results suggest that the beam current and speed function are the most significant processing parameters for non-multispot contouring scanning strategy. While for multispot contouring scanning strategy, the number of spots, spot time, and spot overlap have greater effects than focus offset and beam current. The improved surface roughness has been obtained in both contouring scanning strategies. Furthermore, non-multispot contouring scanning strategy gives a lower surface roughness value and poorer geometrical accuracy than the multispot counterpart under the optimized conditions. These findings could be used as a guideline for selecting the contouring type used for specific industrial parts that are built using EBM. Full article
(This article belongs to the Special Issue Perspectives on Additively Manufactured Metallic Materials)
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Open AccessArticle Predictive Simulation of Process Windows for Powder Bed Fusion Additive Manufacturing: Influence of the Powder Bulk Density
Materials 2017, 10(10), 1117; doi:10.3390/ma10101117
Received: 10 August 2017 / Revised: 19 September 2017 / Accepted: 20 September 2017 / Published: 22 September 2017
PDF Full-text (5815 KB) | HTML Full-text | XML Full-text
Abstract
The resulting properties of parts fabricated by powder bed fusion additive manufacturing processes are determined by their porosity, local composition, and microstructure. The objective of this work is to examine the influence of the stochastic powder bed on the process window for dense
[...] Read more.
The resulting properties of parts fabricated by powder bed fusion additive manufacturing processes are determined by their porosity, local composition, and microstructure. The objective of this work is to examine the influence of the stochastic powder bed on the process window for dense parts by means of numerical simulation. The investigations demonstrate the unique capability of simulating macroscopic domains in the range of millimeters with a mesoscopic approach, which resolves the powder bed and the hydrodynamics of the melt pool. A simulated process window reveals the influence of the stochastic powder layer. The numerical results are verified with an experimental process window for selective electron beam-melted Ti-6Al-4V. Furthermore, the influence of the powder bulk density is investigated numerically. The simulations predict an increase in porosity and surface roughness for samples produced with lower powder bulk densities. Due to its higher probability for unfavorable powder arrangements, the process stability is also decreased. This shrinks the actual parameter range in a process window for producing dense parts. Full article
(This article belongs to the Special Issue Perspectives on Additively Manufactured Metallic Materials)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Effect of thermal field transformation on microstructure in selective laser melting
Authors: Ketai He1*, Shuang Luo1, Yili Hong2*, Zhehan Chen1
Affiliation:
1) School of Mechanical Engineering, University of Science and Technology Beijing, 100083
2) Department of Statistics, Virginia Polytechnic Institute and State University, 24060
Abstract: Considering the environment factors, there are no absolute same pieces in selective laser melting(SLM), so it is difficult to reproduce defaults in product. Because the physical phenomena occur over a broad range of length and time scales and there are so many process parameters in SLM, the time cost and material cost are high to find rules that defaults occur by doing experiments and simulations. Most mechanical properties have strong relationships with microstructure. Microstructure is one important factor that affects the mechanical features of metal part and different transformation of thermal field will result different microstructure. Therefore, in this paper some research work has been done to find the mechanism of microstructure generation in SLM. Some experiments are designed and done to find the effects of thermal field transformation on microstructure in SLM. Firstly, different scanning paths are taken and the thermal field of every layer is recorded; secondly, the microstructures of the parts are got with scanning electron microscope(SEM); thirdly, data mining and statistical analysis technology is used to analyze the effect of thermal field transformation on microstructure.

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