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Mechanical Performance and Structural Integrity of Additive Manufactured Materials
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Mechanical Performance and Structural Integrity of Additive Manufactured Materials

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Manufacturing Processes and Systems".

Deadline for manuscript submissions: closed (20 October 2022) | Viewed by 12136

Special Issue Editors

Prof. Dr. Robert Lancaster

E-Mail Website
Guest Editor
Institute of Structural Materials, Swansea University, Bay Campus, Swansea SA1 8EN, UK
Interests: miniaturised testing; additive manufacturing (AM) processes; nickel superalloys (single crystals, polycrystalline); thermomechanical fatigue (TMF); fatigue lifting; failure analysis
Special Issues, Collections and Topics in MDPI journals
Dr. Spencer Jeffs

E-Mail Website
Guest Editor
Institute of Structural Materials, College of Engineering, Swansea University, Bay Campus, Swansea, UK
Interests: ceramic matrix composites; nickel superalloys; titanium alloys; additive manufacturing; solid state welding processes; mechanical testing; miniaturised testing; failure analysis; material characterisation

Special Issue Information

Dear Colleagues,

Additive manufacturing (AM) encompasses the wide range of processes that consist of “3D printing” of metallic materials and has revolutionised the production capability of high-performance metallic components, offering significant potential for lean manufacture and the ability to produce fully dense near-net shaped parts with highly customised, intricate geometries. However, the metallurgical treatments under which AM materials are processed differ significantly from those manufactured through more traditional methods, such as casting or forging. This can lead to the formation of adverse microstructures and structural defects, which in turn can inhibit the materials’ mechanical performance. Therefore, it is of significant importance to academic and industrial scientists to focus their research and development activities on understanding how the mechanical potential of AM materials can be fully realised.

It is my pleasure to invite you to submit original contributions that may take into account any of the materials aspects involved in the understanding of the structural and mechanical performance of AM components. This may consider, among others, the effects of alloy powder chemistry and condition, process parameters and strategies, processing defects, and post-process thermomechanical treatments on the performance of the final component.

Prof. Dr. Robert Lancaster
Dr. Spencer Jeffs
Guest Editors

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. Materials is an international peer-reviewed open access semimonthly 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
  • mechanical properties
  • structural integrity
  • laser powder bed fusion
  • direct energy deposition
  • process parameters
  • material defects
  • microstructural analysis
  • deformation behaviour

Published Papers (5 papers)

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Research

18 pages, 5217 KiB  
Article
Effect of Internal Defects on the Fatigue Behavior of Additive Manufactured Metal Components: A Comparison between Ti6Al4V and Inconel 718
by Nicola Cersullo, Jon Mardaras, Philippe Emile, Katja Nickel, Vitus Holzinger and Christian Hühne
Materials 2022, 15(19), 6882; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15196882 - 03 Oct 2022
Cited by 12 | Viewed by 1867
Abstract
In order to obtain a widespread application of Additive Manufactured (AM) technology in the aircraft industry for fatigue critical parts, a detailed characterization of the Fatigue and Damage Tolerance (F&DT) behavior of structural components is required. Metal AM techniques in particular are prone [...] Read more.
In order to obtain a widespread application of Additive Manufactured (AM) technology in the aircraft industry for fatigue critical parts, a detailed characterization of the Fatigue and Damage Tolerance (F&DT) behavior of structural components is required. Metal AM techniques in particular are prone to internal defects inherently present due to the nature of the process, which have a detrimental effect on fatigue properties. In the present work, Ti6Al4V and Inconel 718 coupons with artificially induced defects of different dimensions were produced by the Laser Powder Bed Fusion (LPBF) technique. Fatigue tests were performed, and a different defect sensitiveness was observed between the two materials with Inconel being more defect tolerant compared to Titanium. The environmental role at the crack tip of internal defects was discussed, and based on a purely fracture mechanics approach, a simplified stress–life–defect size model was finally devised. The experimental test results together with the information obtained from the fracture surface analysis of tested samples are used to validate the model predictions. The proposed approach could be adopted to define a critical defect size map to be used for tailored Non-Destructive Testing (NDT) evaluation. Full article
(This article belongs to the Special Issue Mechanical Performance and Structural Integrity of Additive Manufactured Materials)
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24 pages, 8273 KiB  
Article
Aging Profiles of AlSi7Mg0.6 and AlSi10Mg0.3 Alloys Manufactured via Laser-Powder Bed Fusion: Direct Aging versus T6
by Emanuela Cerri and Emanuele Ghio
Materials 2022, 15(17), 6126; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15176126 - 03 Sep 2022
Cited by 8 | Viewed by 1507
Abstract
The artificial aging heat treatments performed directly on as-built and solubilized AlSi7Mg0.6 and AlSi10Mg0.3 samples were characterized and discussed. The analysed bars and billets (height of 300 mm) were manufactured via the Laser Powder-Bed Fusion process on a build platform heated at 150 [...] Read more.
The artificial aging heat treatments performed directly on as-built and solubilized AlSi7Mg0.6 and AlSi10Mg0.3 samples were characterized and discussed. The analysed bars and billets (height of 300 mm) were manufactured via the Laser Powder-Bed Fusion process on a build platform heated at 150 °C. Therefore, its influence on the as-built samples was studied in terms of mechanical performance variations between the bottom and top regions. Vickers microhardness measurements were performed to obtain aging profiles after direct aging (175–225 °C) and T6 heat treatments and to highlight better time and temperature parameters to optimize the mechanical properties of both alloys. SEM observations were used to characterize the microstructure before and after the heat treatments and its influence on the fracture mechanisms. Generally, the direct aging heat treatments show the same effects on both aluminium alloys, unlike the solubilization at 505 °C followed by artificial aging at 175 °C. The strengths vs. elongation values obtained after the direct aging treatments are better than those exhibited by T6 as highlighted by the quality index. Full article
(This article belongs to the Special Issue Mechanical Performance and Structural Integrity of Additive Manufactured Materials)
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22 pages, 15488 KiB  
Article
Effects of Annealing and Solution Treatments on the Microstructure and Mechanical Properties of Ti6Al4V Manufactured by Selective Laser Melting
by Hassanen Jaber, János Kónya, Klaudia Kulcsár and Tünde Kovács
Materials 2022, 15(5), 1978; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15051978 - 07 Mar 2022
Cited by 20 | Viewed by 3586
Abstract
Ti6Al4V (Ti64) alloys manufactured by selective laser melting (SLM) are well known for their susceptibility to failure at a low ductility of less than 10% due to the formation of an (α′) martensitic structure. Annealing and solution treatments as post-heat treatments of α′ [...] Read more.
Ti6Al4V (Ti64) alloys manufactured by selective laser melting (SLM) are well known for their susceptibility to failure at a low ductility of less than 10% due to the formation of an (α′) martensitic structure. Annealing and solution treatments as post-heat treatments of α′ are considered a good way to improve the mechanical performance of SLM-manufactured Ti64 parts. In this research, the effect of heat treatment parameters such as temperature (850 °C and 1020 °C) and cooling rate (furnace and water cooling) on the microstructure and mechanical properties of the SLM Ti64 structure was investigated. It was shown that the tensile strength/ductility of the Ti64 alloy produced by SLM was determined by the post-heat treatment. The experimental results revealed that heat treatment at 850 °C followed by furnace cooling resulted in the best possible combination of ductility (13%) and tensile strength (σy = 932, σu = 986 MPa) with a microstructure consisting mainly of 78.71% α and 21.29% β. Heat treatment at 850 °C followed by water cooling was characterized by a reduction in hardness and the formation of predominantly α plus α′′ and a small amount of β. HT850WC exhibited yield and tensile strengths of about 870 and 930 MPa, respectively, and an elongation at fracture of 10.4%. Heat treatment at 1020 °C and subsequent cooling in the furnace was characterized by the formation of an α + β lamellar microstructure. In contrast, heat treatment at 1020 °C and subsequent water cooling formed semi-equiaxial β grains of about 170 µm in diameter with longer elongated α grains and basket-weave α′. Post-treatment at 1020 °C followed by furnace cooling showed high ductility with an elongation of 14.5% but low tensile strength (σy = 748, σu = 833 MPa). In contrast, post-treatment at 1020 °C followed by water cooling showed poor ductility with elongation of 8.6% but high tensile strength (σy = 878, σu = 990 MPa). The effect of aging at 550 °C for 3 h and cooling in a furnace on the microstructure and mechanical properties of the specimens cooled with water was also studied. It was found that aging influenced the microstructure of the Ti6Al4V parts, including β, α, and α″ precipitation and fragmentation or globularization of elongated α grains. The aging process at 550 °C leads to an increase in tensile strength and a decrease in ductility. Full article
(This article belongs to the Special Issue Mechanical Performance and Structural Integrity of Additive Manufactured Materials)
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12 pages, 4607 KiB  
Article
Effect of Process Parameters and Build Orientation on Microstructure and Impact Energy of Electron Beam Powder Bed Fused Ti-6Al-4V
by Spencer Jeffs, Robert Lancaster, Gareth Davies, William Hole, Brenna Roberts, David Stapleton, Meurig Thomas, Iain Todd and Gavin Baxter
Materials 2021, 14(18), 5376; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14185376 - 17 Sep 2021
Cited by 2 | Viewed by 1998
Abstract
To fully exploit the benefits of additive manufacturing (AM), an understanding of its processing, microstructural, and mechanical aspects, and their interdependent characteristics, is necessary. In certain instances, AM materials may be desired for applications where impact toughness is a key property, such as [...] Read more.
To fully exploit the benefits of additive manufacturing (AM), an understanding of its processing, microstructural, and mechanical aspects, and their interdependent characteristics, is necessary. In certain instances, AM materials may be desired for applications where impact toughness is a key property, such as in gas turbine fan blades, where foreign or direct object damage may occur. In this research, the impact energy of a series of Ti-6Al-4V specimens produced via electron beam powder bed fusion (EBPBF) was established via Charpy impact testing. Specimens were produced with five different processing parameter sets, in both the vertical and horizontal build orientation, with microstructural characteristics of prior β grain area, prior β grain width, and α lath width determined in the build direction. The results reveal that horizontally oriented specimens have a lower impact energy compared to those built in the vertical orientation, due to the influence of epitaxial grain growth in the build direction. Relationships between process parameters, microstructural characteristics, and impact energy results were evaluated, with beam velocity displaying the strongest trend in terms of impact energy results, and normalised energy density exhibiting the most significant influence across all microstructural measurements. Full article
(This article belongs to the Special Issue Mechanical Performance and Structural Integrity of Additive Manufactured Materials)
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12 pages, 3079 KiB  
Article
The Effects of Overhang Forming Direction on Thermal Behaviors during Additive Manufacturing Ti-6Al-4V Alloy
by Fan Wu, Zhonggang Sun, Wei Chen and Zulei Liang
Materials 2021, 14(13), 3749; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14133749 - 05 Jul 2021
Cited by 5 | Viewed by 2355
Abstract
Selective laser melting was recently introduced to fabricate complex parts that are likely to contain overhangs. Process parameters, scanning strategies, support structures, and fast prediction techniques are being frequently studied, but little information about overhang forming direction has been reported. In this study, [...] Read more.
Selective laser melting was recently introduced to fabricate complex parts that are likely to contain overhangs. Process parameters, scanning strategies, support structures, and fast prediction techniques are being frequently studied, but little information about overhang forming direction has been reported. In this study, the effects of overhang forming direction in the working plane on temperature evolution and distortion processes during selective laser melting of Ti-6Al-4V alloy were examined by means of numerical simulation and experimental verification. We found that forming from different directions can lead to significant differences in the early stage of the overhang building process, which were verified by both the simulations and the experiment. Some analyses were performed when enough layers had been built and suggestions are also given. Full article
(This article belongs to the Special Issue Mechanical Performance and Structural Integrity of Additive Manufactured Materials)
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