Special Issue "Additive Manufacturing of Metals"

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

Deadline for manuscript submissions: 31 December 2019

Special Issue Editor

Guest Editor
Prof. Gregory John Gibbons

WMG, International Manufacturing Centre, University of Warwick, Coventry, CV4 7AL, United Kingdom
Website | E-Mail
Phone: 0044 2476522524
Interests: additive layer manufacturing; rapid prototyping; rapid tooling; novel coatings; materials development; advanced ceramics synthesis and processing

Special Issue Information

Dear Colleagues,

Metals Additive Manufacturing (AM) is a rapidly growing manufacturing capability. The cumulative annual growth of AM is predicted to exceed 20% CAGR for many years to come, reaching $9 billion in 2017 and expected to rise to over $63 billion by 2025. The metals (AM) market is particularly buoyant, rising 41% CAGR over 2010–2014. Current metal AM service market is £100 m, projected to reach £590 million by 2020 (CAGR of 31.5%), with increasing application in the aerospace and defense industry. Despite this remarkable rate of growth, there are significant challenges that are limiting the wider uptake and exploitation of metals AM, spanning across the entire metal AM supply chain. These include a lack of AM design and modelling skills and software, a gap in understanding in properties obtained from different machines and technologies, and an incomplete understanding of the causes of part quality variation and their effect on part failure. For this Special Issue in Metals we welcome reviews and articles in the areas of material supply, part design, process modelling, process technology, post-processing techniques and applications of metals AM.

Prof. Gregory John Gibbons
Guest Editor

Manuscript Submission Information

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Keywords

  • metals additive manufacturing
  • metal powders
  • metallurgy
  • design
  • manufacturing
  • thermal modelling
  • mechanical modelling
  • powder bed fusion
  • directed energy deposition
  • binder jetting

Published Papers (6 papers)

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Research

Open AccessArticle
The Relationship of Fracture Mechanism between High Temperature Tensile Mechanical Properties and Particle Erosion Resistance of Selective Laser Melting Ti-6Al-4V Alloy
Metals 2019, 9(5), 501; https://doi.org/10.3390/met9050501
Received: 22 March 2019 / Revised: 8 April 2019 / Accepted: 26 April 2019 / Published: 29 April 2019
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Abstract
In this study, selective laser melting (SLM) Ti-6Al-4V is subjected to heat treatment for 4 h at 400 °C, 600 °C, and 800 °C, followed by air cooling. After heat treatment at 400 °C and 600 °C, the ductility was lower (strength increased). [...] Read more.
In this study, selective laser melting (SLM) Ti-6Al-4V is subjected to heat treatment for 4 h at 400 °C, 600 °C, and 800 °C, followed by air cooling. After heat treatment at 400 °C and 600 °C, the ductility was lower (strength increased). This was could be for two reasons: (1) high temperature tensile properties, and (2) particle erosion wear induced phase transformation. Finally, the particle erosion rates of as-SLM Ti-6Al-4V and heat treatment for 4 h at 800 °C (labeled 800-AC) were investigated and compared; the lamellar α + β phases in 800-AC are difficult to destroy with erosion particles, resulting in the erosion resistance of 800-AC being higher than that of the martensitic α’ needles in the as-SLM Ti-6Al-4V at all impact angles (even the hardness of the 800-AC specimen was lower). The as-SLM Ti-6Al-4V alloy needs heat treatment to have better wear resistance. Full article
(This article belongs to the Special Issue Additive Manufacturing of Metals)
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Open AccessArticle
Effect of Fe Addition on Heat-Resistant Aluminum Alloys Produced by Selective Laser Melting
Metals 2019, 9(4), 468; https://doi.org/10.3390/met9040468
Received: 26 March 2019 / Revised: 13 April 2019 / Accepted: 20 April 2019 / Published: 22 April 2019
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Abstract
The effect of Fe addition on the high-temperature mechanical properties of heat-resistant aluminum alloys produced by selective laser melting (SLM) was investigated in relation to the alloy microstructures. Fe is generally detrimental to the properties of cast aluminum alloys; however, we found that [...] Read more.
The effect of Fe addition on the high-temperature mechanical properties of heat-resistant aluminum alloys produced by selective laser melting (SLM) was investigated in relation to the alloy microstructures. Fe is generally detrimental to the properties of cast aluminum alloys; however, we found that Fe-containing alloys produced by SLM had improved high-temperature strength and good ductility. Microstructural observations revealed that the increase in the high-temperature strength of the alloys was due to the dispersion of fine rod-shaped Fe-Si-Ni particles unique to the SLM material instead of the cell-like structure of eutectic Si. Full article
(This article belongs to the Special Issue Additive Manufacturing of Metals)
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Open AccessArticle
The Size Effect on Forming Quality of Ti–6Al–4V Solid Struts Fabricated via Laser Powder Bed Fusion
Metals 2019, 9(4), 416; https://doi.org/10.3390/met9040416
Received: 4 March 2019 / Revised: 31 March 2019 / Accepted: 3 April 2019 / Published: 6 April 2019
Cited by 1 | PDF Full-text (15593 KB) | HTML Full-text | XML Full-text
Abstract
Laser powder bed fusion (LPBF) is useful for manufacturing complex structures; however, factors affecting the forming quality have not been clearly researched. This study aimed to clarify the influence of geometric characteristic size on the forming quality of solid struts. Ti–6Al–4V struts with [...] Read more.
Laser powder bed fusion (LPBF) is useful for manufacturing complex structures; however, factors affecting the forming quality have not been clearly researched. This study aimed to clarify the influence of geometric characteristic size on the forming quality of solid struts. Ti–6Al–4V struts with a square section on the side length (0.4 to 1.4 mm) were fabricated with different scan speeds. Micro-computed tomography was used to detect the struts’ profile error and defect distribution. Scanning electron microscopy and light microscopy were used to characterize the samples’ microstructure. Nanoindentation tests were conducted to evaluate the mechanical properties. The experimental results illustrated that geometric characteristic size influenced the struts’ physical characteristics by affecting the cooling condition. This size effect became obvious when the geometric characteristic size and the scan speed were both relatively small. The solid struts with smaller geometric characteristic size had more obvious size error. When the geometric characteristic size was smaller than 1 mm, the nanohardness and elastic modulus increased with the increase in scan speed, and decreased with the decline of the geometric characteristic size. Therefore, a relatively high scan speed should be selected for LPBF—the manufacturing of a porous structure, whose struts have small geometric characteristic size. Full article
(This article belongs to the Special Issue Additive Manufacturing of Metals)
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Open AccessArticle
Experiment of Process Strategy of Selective Laser Melting Forming Metal Nonhorizontal Overhanging Structure
Metals 2019, 9(4), 385; https://doi.org/10.3390/met9040385
Received: 9 March 2019 / Revised: 23 March 2019 / Accepted: 25 March 2019 / Published: 27 March 2019
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Abstract
To improve the precision of the nonhorizontal suspension structure and the forming quality of the overhanging surface by selective laser melting, the influence of laser power on the upper surface and the overhanging surface forming quality of 316L stainless steel at different forming [...] Read more.
To improve the precision of the nonhorizontal suspension structure and the forming quality of the overhanging surface by selective laser melting, the influence of laser power on the upper surface and the overhanging surface forming quality of 316L stainless steel at different forming angles was studied in the experiment. The influence of different scanning strategies, upper surface remelting optimization, and overhang boundary scanning optimization on the formation of overhanging structures was compared and analyzed. The forming effect of chromium–nickel alloy is better than 316L stainless steel below the limit forming angle in the overhanging structure. The better forming effect of chromium–nickel alloy can be obtained by narrowing the hatch space with the boundary optimization process. The experiment results show that the forming of the overhanging structure below the limit forming angle should adopt the chessboard scanning strategy. The smaller laser power remelting is beneficial to both the forming of the overhanging surface and the quality of upper surface forming. The minimum value of surface roughness using the 110 W power laser twice during surface remelting and boundary scanning 75° overhanging surface can reach 11.9 μm and 31.1 μm, respectively. The forming accuracy error range above the limit forming angle is controlled within 0.4 mm, and the forming quality is better. A boundary count scanning strategy was applied to this study to obtain lower overhanging surface roughness values. This research proposes a process optimization and improvement method for the nonhorizontal suspension structure formed by selective laser melting, which provides the process support for practical application. Full article
(This article belongs to the Special Issue Additive Manufacturing of Metals)
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Open AccessCommunication
Comparison of Nano-Mechanical Behavior between Selective Laser Melted SKD61 and H13 Tool Steels
Metals 2018, 8(12), 1032; https://doi.org/10.3390/met8121032
Received: 8 November 2018 / Revised: 3 December 2018 / Accepted: 4 December 2018 / Published: 6 December 2018
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Abstract
Using nanoindentation under various strain rates, the mechanical properties of a laser powder bed fusion (PBF) SKD61 at the 800 mm/s scan speed were investigated and compared to PBF H13. No obvious pile-up due to the ratio of the residual depth (h [...] Read more.
Using nanoindentation under various strain rates, the mechanical properties of a laser powder bed fusion (PBF) SKD61 at the 800 mm/s scan speed were investigated and compared to PBF H13. No obvious pile-up due to the ratio of the residual depth (hf) and the maximum depth (hmax) being lower than 0.7 and no cracking were observed on any of the indenter surfaces. The nanoindentation strain-rate sensitivity (m) of PBF SKD61 was found to be 0.034, with hardness increasing from 8.65 GPa to 9.93 GPa as the strain rate increased between 0.002 s−1 and 0.1 s−1. At the same scan speed, the m value of PBF H13 (m = 0.028) was lower than that of PBF SKD61, indicating that the mechanical behavior of PBF SKD61 was more critically affected by the strain rate compared to PBF H13. PBF processing for SKD61 therefore shows higher potential for advanced tool design than for H13. Full article
(This article belongs to the Special Issue Additive Manufacturing of Metals)
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Open AccessArticle
Additive Manufactured A357.0 Samples Using the Laser Powder Bed Fusion Technique: Shear and Tensile Performance
Metals 2018, 8(9), 670; https://doi.org/10.3390/met8090670
Received: 26 July 2018 / Revised: 13 August 2018 / Accepted: 24 August 2018 / Published: 27 August 2018
Cited by 2 | PDF Full-text (9545 KB) | HTML Full-text | XML Full-text
Abstract
New aluminium alloys, with lower silicon content than in the first-developed formulations, have recently been introduced in the field of Additive Manufacturing and are dedicated to automotive applications. As they are relatively new, mechanical characterization under standard protocols of the automotive field are [...] Read more.
New aluminium alloys, with lower silicon content than in the first-developed formulations, have recently been introduced in the field of Additive Manufacturing and are dedicated to automotive applications. As they are relatively new, mechanical characterization under standard protocols of the automotive field are of utmost scientific as well as industrial relevance. The paper addresses the mechanical properties and microstructure of A357.0. Static tensile and shear tests of samples built by Laser Powder Bed Fusion, with different orientations in the machine work volume, have been performed. The aim was to identify possible anisotropy in the tensile and shear behaviour of this innovative alloy. Particularly for shear, the effect of adhesion between the layers onto shear strength was studied. Results analysis, by means of statistical tools, allows for the affirmation that no tensile modulus or yield strength anisotropy is observed. Instead, a small (yet statistically significant) increase in both shear- and tensile strength and a decrease in ductility are obtained as the direction of the specimens approaches the growth direction. Scanning Electron Microscope (SEM) observation of the failure mechanisms assisted in the interpretation of the results, by relating different failure modes to the relative orientation of loads versus the directions of inherent anisotropy in Laser Powder Bed Fusion processes. Full article
(This article belongs to the Special Issue Additive Manufacturing of Metals)
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Graphical abstract

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