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Microstructural, Functional and Mechanical Properties of Metallic Materials Processed by Additive Manufacturing

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

Deadline for manuscript submissions: closed (30 September 2019) | Viewed by 8718

Special Issue Editor


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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) technologies allow producing complex parts by means of a direct or layer-wise addition of material starting from CAD models. AM technologies were initially developed for producing prototypes, but over the years their use has been extended to fabricate functional and structural components for service in several industrial fields.

Solidification in materials processed by beam-based AM technologies usually occurs very rapidly, out of equilibrium, and leads to the formation of extended solid solutions, fine cellular microstructures, and crystallographic textures. Non-beam-based AM technologies typically use organic binders and additives to assemble metal powders. Debinding and sintering operations are needed to achieve high-density parts. Post-process heat treatments not only have a strong effect on the shrinkage behavior and residual porosity of AM parts but also lead to different microstructures. Thus, in order to maximize the performance of AM components, it is of primary importance to tailor alloy formulations and heat treatments.

It is my pleasure to invite you to submit contributions to this Special Issue on the correlation between process parameters, microstructures, and properties of alloys produced by AM, focusing on your most important findings, highlighting future challenges, and providing new perspectives.

Prof. Dr. Riccardo Casati
Guest Editor

Manuscript Submission Information

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Keywords

  • Metallurgy
  • Additive Manufacturing
  • Microstructures
  • Mechanical properties
  • Functional properties

Published Papers (3 papers)

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Research

22 pages, 10511 KiB  
Article
Tool Life Performance of Injection Mould Tooling Fabricated by Selective Laser Melting for High-Volume Production
by Mennatallah F. El Kashouty, Allan E. W. Rennie and Mootaz Ghazy
Materials 2019, 12(23), 3910; https://doi.org/10.3390/ma12233910 - 26 Nov 2019
Cited by 8 | Viewed by 3106
Abstract
Rapid Tooling processes are developing and proving to be a reliable method to compete with subtractive techniques for tool making. This paper investigates large volume production of components produced from Selective Laser Melting (SLM) fabricated injection moulding tool inserts. To date, other researchers [...] Read more.
Rapid Tooling processes are developing and proving to be a reliable method to compete with subtractive techniques for tool making. This paper investigates large volume production of components produced from Selective Laser Melting (SLM) fabricated injection moulding tool inserts. To date, other researchers have focused primarily on investigating the use of additive manufacturing technology for injection moulding for low-volume component production rather than high volume production. In this study, SLM technology has been used to fabricate four Stainless Steel 316L tool inserts of a similar geometry for an after-market automotive spare part. The SLM tool inserts have been evaluated to analyse the maximum number of successful injections and quality of performance. Microstructure inspection and chemical composition analysis have been investigated. Performance tests were conducted for the four tool inserts before and after injection moulding in the context of hardness testing and dimensional accuracy. For the first reported time, 150,000 injected products were successfully produced from the four SLM tool inserts. Tool inserts performance was monitored under actual operating conditions considering high-level demands. In the scope of this research, SLM proved to be a dependable manufacturing technique for most part geometries and an effective alternative to subtractive manufacturing for high-volume injection moulding tools for the aftermarket automotive sector. Full article
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16 pages, 9770 KiB  
Article
Formability of Ultrasonically Additive Manufactured Ti-Al Thin Foil Laminates
by İrfan Kaya, Ömer Necati Cora and Muammer Koç
Materials 2019, 12(20), 3402; https://doi.org/10.3390/ma12203402 - 17 Oct 2019
Cited by 2 | Viewed by 2169
Abstract
This study investigates the effect of strain rates and temperatures on the mechanical behavior of ultrasonically consolidated Titanium–Aluminum thin foils to understand and characterize their formability. To this goal, laminated composite samples with a distinct number of layers were bonded using ultrasonic consolidation. [...] Read more.
This study investigates the effect of strain rates and temperatures on the mechanical behavior of ultrasonically consolidated Titanium–Aluminum thin foils to understand and characterize their formability. To this goal, laminated composite samples with a distinct number of layers were bonded using ultrasonic consolidation. Then, tensile and biaxial hydraulic bulge tests at different strain rates and temperature conditions were conducted. The effect of the sample orientation on the mechanical response was also examined. Tensile and hydraulic bulge tests results were compared to observe differences in ultimate tensile strength and strain levels under uniaxial and biaxial loading conditions. The effects of loading condition, strain rate, and temperature on the material response were analyzed and discussed on the basis of test results. In general, it was concluded that the maximum elongation values attained were higher for the samples subtracted along the sonotrode movement direction compared to those obtained from the normal to sonotrode movement direction. The elongation was obtained as high as 46% for seven bi-layered samples at high-temperature ranges of 200–300 °C. Hydraulic bulge test results showed that elongation improved as the number of bi-layers increased, yet the ultimate strength values did not change significantly indicating an expansion of the formability window. Full article
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12 pages, 7089 KiB  
Article
Hydrogen Embrittlement Behavior of 18Ni 300 Maraging Steel Produced by Selective Laser Melting
by Young Jin Kwon, Riccardo Casati, Mauro Coduri, Maurizio Vedani and Chong Soo Lee
Materials 2019, 12(15), 2360; https://doi.org/10.3390/ma12152360 - 25 Jul 2019
Cited by 12 | Viewed by 3067
Abstract
A study was performed to investigate the hydrogen embrittlement behavior of 18-Ni 300 maraging steel produced by selective laser melting and subjected to different heat treatment strategies. Hydrogen was pre-charged into the tensile samples by an electro-chemical method at the constant current density [...] Read more.
A study was performed to investigate the hydrogen embrittlement behavior of 18-Ni 300 maraging steel produced by selective laser melting and subjected to different heat treatment strategies. Hydrogen was pre-charged into the tensile samples by an electro-chemical method at the constant current density of 1 A m−2 and 50 A m−2 for 48 h at room temperature. Charged and uncharged specimens were subjected to tensile tests and the hydrogen concentration was eventually analysed using quadrupole mass spectroscopy. After tensile tests, uncharged maraging samples showed fracture surfaces with dimples. Conversely, in H-charged alloys, quasi-cleavage mode fractures occurred. A lower concentration of trapped hydrogen atoms and higher elongation at fracture were measured in the H-charged samples that were subjected to solution treatment prior to hydrogen charging, compared to the as-built counterparts. Isothermal aging treatment performed at 460 °C for 8 h before hydrogen charging increased the concentration of trapped hydrogen, giving rise to higher hydrogen embrittlement susceptibility. Full article
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