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Metals
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Microstructure and Mechanical Properties of Metallic Alloys Produced by Additive...
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Microstructure and Mechanical Properties of Metallic Alloys Produced by Additive Manufacturing

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (30 June 2018) | Viewed by 22936

Special Issue Editor

Prof. Dr. Maurizio Vedani

E-Mail Website
Guest Editor
Department of Mechanical Engineering, Politecnico di Milano, Via Giuseppe La Masa 1, 20156 Milano, Italy
Interests: material science; metallurgy; additive manufacturing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Additive manufacturing (AM) of metals is revolutionizing the way of conceiving parts and structures. It enables a high degree of design freedom, allowing the production of objects with optimized shapes for specific applications. Several processes have been developed in the last few decades, belonging the group of Additive Layer Manufacturing (e.g., selective laser melting, electron beam melting) and to that of Direct Metal Deposition.

From the material perspective, the peculiar solidification conditions induced by AM processes allow to generate specific microstructures and properties that still need to be investigated deeply. In addition, large opportunities are available for the design of new dedicated alloys showing an improved ability to be processed, as well as higher performances.

The aim of this Special Issue is to highlight recent innovations related to additive manufacturing of metals with a special emphasis on new properties and innovative materials tailored for this processing technique.

Prof. Dr. Maurizio  Vedani
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
  • selective laser melting
  • electron beam melting
  • direct metal deposition
  • microstructure
  • texture
  • mechanical behavior
  • solidification condition

Published Papers (4 papers)

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Research

12 pages, 13855 KiB  
Article
Effect of Powder Feedstock on Microstructure and Mechanical Properties of the 316L Stainless Steel Fabricated by Selective Laser Melting
by Wei Chen, Guangfu Yin, Zai Feng and Xiaoming Liao
Metals 2018, 8(9), 729; https://doi.org/10.3390/met8090729 - 17 Sep 2018
Cited by 42 | Viewed by 6410
Abstract
Additive manufacturing by selective laser melting (SLM) was used to investigate the effect of powder feedstock on 316L stainless steel properties include microstructure, relative density, microhardness and mechanical properties. Gas atomized SS316L powders of three different particle size distribution were used in this [...] Read more.
Additive manufacturing by selective laser melting (SLM) was used to investigate the effect of powder feedstock on 316L stainless steel properties include microstructure, relative density, microhardness and mechanical properties. Gas atomized SS316L powders of three different particle size distribution were used in this study. Microstructural investigations were done by scanning electron microscopy (SEM). Tensile tests were performed at room temperatures. Microstructure characterization revealed the presence of hierarchical structures consisting of solidified melt pools, columnar grains and multiform shaped sub-grains. The results showed that the SLM sample from the fine powder obtained the highest mechanical properties with ultimate tensile strength (UTS) of 611.9 ± 9.4 MPa and yield strength (YS) of 519.1 ± 5.9 MPa, and an attendant elongation (EL) of 14.6 ± 1.9%, and a maximum of 97.92 ± 0.13% and a high microhardness 291 ± 6 HV0.1. It has been verified that the fine powder (~16 μm) could be used in additive manufacturing with proper printing parameters. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Metallic Alloys Produced by Additive Manufacturing)
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17 pages, 8440 KiB  
Article
Research on Selective Laser Melting of Ti6Al4V: Surface Morphologies, Optimized Processing Zone, and Ductility Improvement Mechanism
by Di Wang, Wenhao Dou and Yongqiang Yang
Metals 2018, 8(7), 471; https://doi.org/10.3390/met8070471 - 21 Jun 2018
Cited by 34 | Viewed by 5945
Abstract
The quality and mechanical properties of titanium alloy fabricated using selective laser melting (SLM) are critical to the adoption of the process which has long been impeded by the lack of uniformity in SLM-fabrication parameter optimization. In order to address this problem, laser [...] Read more.
The quality and mechanical properties of titanium alloy fabricated using selective laser melting (SLM) are critical to the adoption of the process which has long been impeded by the lack of uniformity in SLM-fabrication parameter optimization. In order to address this problem, laser power and scanning speed were combined into linear energy density as an independent variable, while surface morphology was defined as a metric. Based on full-factor experiments, the surface quality of SLM-fabricated titanium alloy was classified into five zones: severe over-melting zone, high-energy density nodulizing zone, smooth forming zone, low-energy density nodulizing zone, and sintering zone. The mechanism resulting in the creation of each zone was analyzed. Parameter uniformity was achieved by establishing a parameter window for each zone, and it also revealed that under smooth forming conditions, the relationship of linear energy density to the quality of the formed surface is not linear. It was also found that fabrication efficiency could be improved in the condition of the formation of a smooth surface by increasing laser power and scanning speed. In addition, maximum elongation of the SLM-fabricated titanium alloy increased when the densified parts were processed using an appropriate heat treatment, from a low value of 5.79% to 10.28%. The mechanisms of change in ductility of the alloy were thoroughly analyzed from the perspectives of surface microstructure and fracture morphology. Results indicate that after heat treatment, the microcosmic structure of the alloy was converted from acicular martensite α’ phase to a layered α+β double-phase structure, the fracture type also changed from quasi-cleavage to ductile fracture. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Metallic Alloys Produced by Additive Manufacturing)
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Graphical abstract

12 pages, 18056 KiB  
Article
Laser Powder Bed Fusion of a High Strength Al-Si-Zn-Mg-Cu Alloy
by Alberta Aversa, Giulio Marchese, Diego Manfredi, Massimo Lorusso, Flaviana Calignano, Sara Biamino, Mariangela Lombardi, Paolo Fino and Matteo Pavese
Metals 2018, 8(5), 300; https://doi.org/10.3390/met8050300 - 26 Apr 2018
Cited by 37 | Viewed by 5661
Abstract
Al-Si-Zn-Mg-Cu samples were produced using Laser Powder Bed Fusion from mixed AlSi10Mg and 7075 powders. It was observed that the introduction of silicon to an Al-Zn-Mg-Cu alloy strongly reduced the crack density, probably because of the reduction of the solidification range, the improved [...] Read more.
Al-Si-Zn-Mg-Cu samples were produced using Laser Powder Bed Fusion from mixed AlSi10Mg and 7075 powders. It was observed that the introduction of silicon to an Al-Zn-Mg-Cu alloy strongly reduced the crack density, probably because of the reduction of the solidification range, the improved fluidity of the molten phase and the reduction of the coefficient of thermal expansion. The density measurements showed that crack-free samples can be successfully produced with this powder mixture. The obtained Al-Si-Zn-Mg-Cu samples were characterized in terms of microstructure, hardness and tensile properties showing that this composition is very promising for future powder bed additive manufacturing processes. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Metallic Alloys Produced by Additive Manufacturing)
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16 pages, 11052 KiB  
Article
Sliding Contact Wear Damage of EBM built Ti6Al4V: Influence of Process Induced Anisotropic Microstructure
by Jae Joong Ryu, Sanjay Shrestha, Guha Manogharan and Jai K. Jung
Metals 2018, 8(2), 131; https://doi.org/10.3390/met8020131 - 13 Feb 2018
Cited by 14 | Viewed by 4335
Abstract
Process-induced directional microstructure is identified as one of the key factors of anisotropic mechanical properties. This directional property significantly affects surface contact fatigue and corrosion of electron beam melting (EBM) built biomedical implants. In the current study, material removal on EBM built titanium [...] Read more.
Process-induced directional microstructure is identified as one of the key factors of anisotropic mechanical properties. This directional property significantly affects surface contact fatigue and corrosion of electron beam melting (EBM) built biomedical implants. In the current study, material removal on EBM built titanium (Ti6Al4V) subjected to reciprocating motion of commercially pure titanium spherical slider is investigated to identify the influence of the process-induced layered structure and environments on wear damage. Specimens developed by two different build orientations are mechanically stimulated using different sliding directions with nominally elastic normal load in dry, passivating, and synovial environments. It was noticed that EBM orientation significantly changes wear behavior in ambient environment. Wear resistance of mill-annealed Ti6Al4V was improved in passivating environment. Implications to improve useful life of orthopedic implants are discussed. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Metallic Alloys Produced by Additive Manufacturing)
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