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Zhou et al. J Mater Inf 2022;2:18 https://dx.doi.org/10.20517/jmi.2022.27 Page 3 of 21

[13-24] [31-37]
Figure 1. Room-temperature uniaxial tensile properties of HEAs classified based on their phase types: FCC HEAs ; BCC HEAs ;
[6,38-47]
[9,22,23,25-28]
eutectic HEAs ; PS HEAs . HEAs: high-entropy alloys.
major categories, namely, coherent and incoherent precipitation. Incoherent precipitation includes the
Laves phase (induced by Nb) and topologically close-packed phase (induced by Mo, such as σ and μ
[43,48]
phases) . These precipitates significantly improve the strength of HEAs but deteriorate their ductility.
The sacrificing of ductility can be attributed to the incoherent interface between the HEA matrix and
precipitation, which acts as a source for crack initiation and propagation during deformation. In contrast,
the coherent precipitation, i.e., the L1 -type phase (γ'), potentially produces a prominent strengthening effect
2
on the matrix without much loss of ductility at cryogenic, room or elevated temperatures. For example, the
addition of Ti and Al to FeCoNi can induce a high-content L1 phase within the FCC matrix, leading to
2
[6]
increases in yield strength from ~200 to 1000 MPa, while maintaining a good ductility over 30% .
Furthermore, due to the high-entropy effect, some HEAs decorated by the L1 phase exhibit excellent phase
2
[49]
stability at elevated temperatures compared with conventional superalloys .
Additive manufacturing
3D printing, formally known as additive manufacturing (AM), has rapidly changed the scenario of future
manufacturing by offering significant flexibility for designing and fabricating components with customized
[50]
structures in a layer-by-layer manner . AM also provides a flexible method for the in situ design of
desirable microstructures and properties by controlling the metallurgical behavior within the molten
[51,52]
pool . Therefore, this technology shows excellent superiority in fabricating structural and functional
materials to conventional processing methods, such as casting, forging and welding.

To date, many kinds of AM technologies, such as fused deposition modeling (FDM), binder jetting (BJ),
stereolithography (SLA), digital light projection (DLP), powder bed fusion (PBF) and directed energy
deposition (DED), have been developed to fabricate various materials, including polymers, ceramics and
[53]
metals . Metallic parts are usually manufactured by the FDM, BJ, PBF and DED AM methods. The FDM
and BJ processes use binder materials to glue the metallic powders into products, which subsequently go
through multistep heat treatments to remove the binder materials and realize the densification of the parts.
Impurities and defects are inevitable for the samples printed by FDM and BJ methods, leading to