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Crystals
Special Issues
Additive Manufacturing to Tailor New Alloys and/or New Microstructures
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Additive Manufacturing to Tailor New Alloys and/or New Microstructures

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystalline Metals and Alloys".

Deadline for manuscript submissions: closed (30 November 2022) | Viewed by 3479

Special Issue Editors

Prof. Dr. Stéphane Godet

E-Mail Website
Guest Editor
4MAT, Université Libre de Bruxelles, 165/63, Bruxelles, Brussels, Belgium
Interests: physical metallurgy; characterization; phase transformation; additive manufacturing; microstructure control
Dr. Charlotte de Formanoir

E-Mail Website
Guest Editor
Thermomechanical Metallurgy Laboratory (LMTM) – PX Group Chair, École Polytechnique Fédérale de Lausanne (EPFL), CH-2002 Neuchâtel, Switzerland
Interests: additive manufacturing; metals and alloys; powder bed fusion; process-microstructure-properties relationship

Special Issue Information

Dear Colleagues,

Additive manufacturing (AM) includes various technologies for converting numerical models of three-dimensional objects into physical parts in a layer-by-layer manner. This “bottom-up” production paradigm considerably increases design flexibility, enabling the manufacturing of near-net shape parts with complex geometries. Despite its advantages in terms of design freedom, AM presents a variety of limitations: stochastic formation of defects, residual stresses and cracking, and lack of reproducibility in the properties of the consolidated parts. Additionally, lack of control of the material’s thermal history during AM processing impairs microstructure optimization, which can significantly impact the final properties of the part. Material feedstock for AM of metals remains largely restricted to alloys that were initially developed for conventional manufacturing processes and are not necessarily adapted to the specific thermomechanical context of AM, leading to sub-optimal properties in the final printed parts.

Thorough process monitoring, control and optimization, the development of innovative post-process treatments, and the processing of new alloys or of compositionally graded alloys and multi-materials are examples of strategies that can contribute to increasing the final performances of AM parts. From an environmental perspective, expanding both the materials palette and the functionality of AM parts is key to increasing sustainability.

This Special Issue aims to publish a selection of original research articles that address the abovementioned topics and explore the links between process conditions, microstructures, and properties in AM.

Prof. Dr. Stéphane Godet
Dr. Charlotte de Formanoir
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. Crystals 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
  •  powder bed fusion of metals
  •  directed energy deposition
  •  metals and alloys
  •  multimaterials
  •  microstructure
  •  new process strategies
  •  process–structure–property relation
  •  heat treatments
  •  mechanical properties

Published Papers (2 papers)

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Research

11 pages, 2645 KiB  
Article
A Comparative Study of Microstructure and Hot Deformability of a Fe–Al–Ta Iron Aluminide Prepared via Additive Manufacturing and Conventional Casting
by Aliakbar Emdadi and Sabine Weiß
Crystals 2022, 12(12), 1709; https://doi.org/10.3390/cryst12121709 - 24 Nov 2022
Cited by 5 | Viewed by 1222
Abstract
In this work, the microstructure and hot deformation behavior of laser powder bed fusion (L-PBF) and conventionally cast Fe-25Al-1.5Ta (at.%) alloys were compared. The L-PBF builds recrystallized comparably to the as-cast samples during hot deformation. Nevertheless, distinct differences were observed in the flow [...] Read more.
In this work, the microstructure and hot deformation behavior of laser powder bed fusion (L-PBF) and conventionally cast Fe-25Al-1.5Ta (at.%) alloys were compared. The L-PBF builds recrystallized comparably to the as-cast samples during hot deformation. Nevertheless, distinct differences were observed in the flow behavior characteristics between the as-cast and L-PBF samples. The L-PBF builds exhibited lower flow stress than the as-cast material over the entire deformation conditions tested. The average activation energy of hot deformation (Q) of 344 kJ mol−1 was calculated for the L-PBF build and 385 kJ mol−1 for the cast material. The lower Q indicates lower deformation resistance of the L-PBF sample. The peak work hardening rate (θ) in the L-PBF sample (1.72 × 103 MPa) was significantly smaller than that of the as-cast sample (3.02 × 103 MPa), suggesting that the dislocation glide in the L-PBF sample is less hindered during deformation. Possible sources of the observed differences in the deformation behavior between the L-PBF and cast materials will be discussed. Initial and post-deformation microstructures were characterized using an X-ray diffractometer (XRD) and ultra-high-resolution scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX) detector. The C14-(Fe, Al)2Ta Laves phase (P63/mmc) was predominantly formed at the A2 α-(Fe, Al) matrix phase grain boundaries in both the as-cast and L-PBF materials. The XRD results suggest that the ordering transition from B2-FeAl to a D03-Fe3Al phase occurs during casting, but rarely during ultra-high-cooling L-PBF processing. In summary, the L-PBF creates samples that are subject to less work hardening and require less deformation resistance, and thus, can be formed by a lower deformation force. It, in turn, reduces the loads imposed on the tooling and dies during the deformation processing, contributing to less wear and the high durability of dies. Full article
(This article belongs to the Special Issue Additive Manufacturing to Tailor New Alloys and/or New Microstructures)
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15 pages, 22541 KiB  
Article
Effect of Process Parameters on the Microstructure of Aluminum Alloys Made via Ultrasonic Additive Manufacturing
by Gowtham Venkatraman, Leon M. Headings and Marcelo J. Dapino
Crystals 2022, 12(12), 1696; https://doi.org/10.3390/cryst12121696 - 23 Nov 2022
Cited by 2 | Viewed by 1814
Abstract
Ultrasonic additive manufacturing (UAM) has garnered significant interest in the aerospace and automotive industries for its structural lightweighting and multi-material joining capabilities. This paper details the investigation on the effect of process variables on the resultant microstructure of the built-up part using UAM [...] Read more.
Ultrasonic additive manufacturing (UAM) has garnered significant interest in the aerospace and automotive industries for its structural lightweighting and multi-material joining capabilities. This paper details the investigation on the effect of process variables on the resultant microstructure of the built-up part using UAM for aluminum 6061. The degree of recrystallization is quantified, and an energy metric, defined using the Read–Shockley relationship, is used to build an energy map of the welded part. The total energy stored in the resultant weld interface microstructure is quantified as a fraction of the input and is found to be about 0.1%. The width, average grain size, and percentage of High Angle Grain Boundaries (% HAGB) were used to compare microstructures of builds prepared using different processing conditions. Welding subsequent weld layers was not found to affect the previous welded layers. The effect of vibration amplitude and travel speed on the as-built microstructure were investigated, and the width of the interface was found to more than double when the weld amplitude is increased from the threshold value for joining (23 μm) and then stabilize at higher weld amplitudes. A better understanding of the effect of processing parameters on as-welded microstructures will assist parameter selection for UAM. Full article
(This article belongs to the Special Issue Additive Manufacturing to Tailor New Alloys and/or New Microstructures)
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