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Materials Science in Additive Manufacturing Survey of AM reviews

suitable liquid material depending on the powder material is Scopus. Scopus is one of the most used databases, and it
and intended application. includes more papers than the Web of science.
2.5. Directed energy deposition 3.1. Top 10 authors

In directed energy deposition (DED), metallic powder or As shown in Figure 2, Ramakrishna Seeram from National
wire is fed directly into the focal point of an energy beam University of Singapore has the most review papers (21)
to create a molten pool . Laser Engineered Net Shaping published within AM field, followed by Chua Chee Kai
[35]
(LENS), belonging to DED, was first developed at Sandia from Singapore University of Technology and Design, and
National Laboratories in 1995 and commercialized by Yeong Wai Yee from Nanyang Technological University.
Optomec . Parts printed by LENS accommodate graded It is interesting that all the top three authors are from
[36]
multi-materials and allow microstructures with complex Singapore. Researchers may refer their publications to
[37]
inner features . DED systems with wire-fed methods catch up the up-to-date research in the AM field.
[38]
have been achieved , and DED of powder directly has
[39]
also been successful [40,41] . Lasers and electron beams are the 3.2. Top ten journals
most commonly used energy source. Looking at the sources of these review papers (Figure 3), most
of these AM review papers are published in journal Additive
2.6. Vat photopolymerization
Manufacturing, followed by Materials and International
The definition of Vat photopolymerization is an “additive Journal of Advanced Manufacturing Technology. Researchers
manufacturing process in which liquid photopolymer in a may check these journals’ websites to see the state-of-the-
vat is selectively cured by light-activated polymerization” . art developments of AM technologies.
[2]
Vat photopolymerization uses a (liquid) photopolymer
resin which is able to cure (solidify) under a light 3.3. Top 10 affiliations
source [42,43] . Stereolithography (SLA) and digital light As shown in Figure 4, most of the review papers in
processing (DLP) are the most used techniques which additive manufacturing are from Nanyang Technological
belong to Vat photopolymerization. The scanning speed of University, followed by Singapore Centre for 3D Printing.
vat photopolymerization is relatively high and minimum
layer thickness is adjustable depending on the curing 3.4. Top ten countries
depth . Once finishing the printing, post-processing may Looking at the countries of the authors from, United
[44]
be needed, for example, support material removal and/or States has the most review papers in AM, with 756 review
post-curing by further UV exposure. papers published, followed by China with 617 publications

2.7. Sheet lamination (Figure 5).
Sheet lamination is an AM process in which sheets of 3.5. Review papers in the seven AM techniques
material are bonded to form a part . The process works Dividing these review papers into the seven AM techniques
[45]
by scrubbing each layer together with pressure and/or as introduced in section 2, it can be found that most review
binders continuously. In this technique, the raw material papers are about powder bed fusion, and no review paper
typically is paper, metal foil, polymers or composite is found in sheet lamination (Figure 6). This is probably
sheets predominately formed of metal, or ceramic powder because powder bed fusion is the most focused research area
material. Thermal reaction, chemical reaction bonding, within AM, due to its application potential in aerospace,
or ultrasound can be used for binding. The source of engineering, and biomedicine. While, sheet lamination
activation includes localized or large-scale heating, seems a little bit out of focus at this moment. Note that, the
chemical reaction, and ultrasonic transducers. review papers collected in this subsection only consider
3. Analysis and discussion of AM review the broad review in these seven AM techniques, excluding
the review papers focused on a specific topic (e.g., process
papers parameters’ influence, fatigue analysis, and path planning).
This section gives the detailed analysis of review papers For the broad reviews in these seven AM techniques, the
published within the field of AM. Top authors, source most cited papers are listed in Table 1. Readers can check
journals, affiliations of authors, and countries, are these papers based on their interests. Table 2 gives more
discussed. Then, the review papers are analyzed and review papers focusing on the specific topics in each AM
[46]
discussed based on their different focuses, for example, technique. For example, Nohut and Schwentenwein
different AM techniques (as briefly introduced in the focuses on functionally graded materials in vat
previous section) and materials used. The database used photopolymerization, while Xu et al. focuses on drug
[47]

Volume 1 Issue 4 (2022) 3 https://doi.org/10.18063/msam.v1i4.21