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Mooraj et al. J Mater Inf 2023;3:4 https://dx.doi.org/10.20517/jmi.2022.41 Page 3 of 45

Additive manufacturing (AM), also called 3D printing, is a technology to make objects from 3D digital data,
[37]
usually layer upon layer, as opposed to subtractive manufacturing technologies . There exist several types
of AM systems that can be used to produce metal alloys: powder bed systems, powder feed systems, thermal
spray systems, and wire feed systems. In the case of a powder bed system, the feedstock powders are spread
over a flatbed, and a 2D pattern is selectively melted over the bed using either a laser or electron beam as a
[38,39]
heat source . Powder feed systems flow powders through a delivery nozzle using a carrier gas and then
[40,41]
melt the powders onto the substrate as it impacts the substrate using heat from a laser . Thermal spray
3D printing (TS3DP) systems spray heated powders at high velocities onto a substrate leading to bonding
between powder particles as they impact the substrate surface. This allows parts to be built layer by layer
[42]
without the large heating and cooling rates of laser-based techniques . Finally, wire feed systems use metal
wires as feedstock and can use either electric- or plasma-based welding arcs to melt the wire and build a part
layer by layer [43-46] . AM of multiple elemental feedstock powders or wires offers the capability to build large
compositional libraries at bulk length scales. Furthermore, careful control of the printing parameters during
AM, such as laser power and scan speed, allows for tailoring the cooling rates and resulting solidification
microstructures to expand the material development space.

In order to rapidly discover new HEAs with desirable properties, researchers need to utilize an efficient
workflow to leverage the strengths of various design and characterization techniques. Figure 1 illustrates a
typical protocol for high-throughput development of HEAs. First, the elements of interest are selected based
on their fundamental properties and interactions, which are fed into a high-throughput computational
method like machine learning, molecular dynamics, CALculation of PHAse Diagram (CALPHAD), or first-
principles calculations. These computational methods can then predict the bulk materials’ phase formation,
microstructure, and properties for initial screening of potential compositions of interest. Subsequently,
high-throughput manufacturing can be used to fabricate the vast material library and high-throughput
materials characterization enables rapid measurements of the material properties. This review focuses on
high-throughput computational techniques, synthesis methods, and characterization studies that produce
and analyze alloys with reasonable cooling rates at bulk scale. First, this review explores the high-throughput
computational methods that can easily identify the potential compositions that show promising properties
for structural or functional applications. Then, it discusses the high-throughput manufacturing of bulk
compositional libraries encompassing a wide range of potentially interesting alloys by AM. The final section
of this review describes some high-throughput characterization techniques to accelerate screening of
multicomponent metal alloys. This combination of high-throughput methods offers a guideline for
researchers to discover new alloys rapidly and efficiently.

OVERVIEW OF HEAS
Definition of HEAs
There currently exist two well-accepted definitions of HEAs. The first one, referred to as the “compositional
definition”, states that HEAs are alloys with multiple principal elements (at least 5) where each principal
element makes up 5 at. % to 35 at. % of the overall composition [4,48] . The most commonly studied HEA is the
[2,3]
Cantor alloy system which contains equiatomic CoCrFeNiMn, a prime example of this definition .
Figure 2A illustrates this high-entropy region within a ternary phase diagram, with the center of the phase
[49]
diagram covered by the high-entropy region . It should be noted that the edges of the phase diagram in
Figure 2A may contain two or more elements to match the composition definition. Additionally, minor
[50]
elements can be added to a base HEA system to tune its properties further .