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Page 28 of 45 Mooraj et al. J Mater Inf 2023;3:4 https://dx.doi.org/10.20517/jmi.2022.41

Once the library was prepared, each sample was remelted with different laser powers of 200 W, 240 W, and
280 W. Since a higher laser power leads to a lower cooling rate, compositions that maintain glassy
microstructure with higher laser power should have higher GFA. Differential interference contrast (DIC)
imaging under optical microscopy was used to screen for amorphous materials as samples with amorphous
structures show a smooth liquid-like topography under DIC. At the same time, crystalline microstructures
[179]
appear rough . A total of 144 discrete samples were investigated, and 92 were identified as amorphous for
the lowest power. Based on the previously mentioned criteria, the composition with the highest GFA was
Cu Zr Ti , as it showed a high fraction of amorphous microstructure and was located in the center of
51.7
36.7
11.6
the region of compositions that exhibit an amorphous microstructure after remelting at 280 W. It was also
pointed out that this method could be extended to alloy systems with even more components by using pre-
alloyed powders. Thus, the procedure laid out by Tsai et al. illustrates a means to rapidly identify BMGs
with excellent GFA within a given alloy system. In addition to the optimal composition, combinatorial
studies can also be used to rapidly determine optimal printing parameters for a given alloy system. Islam et
al. carried out such a study on 25 different compositions in the Fe-Ni-Cr-Mo alloy system to and define a
normalized dimensionless parameter based on the energy input density from the laser and the material
[180]
properties of the constituent atoms . A schematic illustration of their experimental method is illustrated
in Figure 13D.

Eutectic HEAs (EHEAs) combine design concepts from both HEAs and eutectic alloys and show great
potential for structural applications due to their impressive combination of strength and ductility [156,181] . This
combination of properties arises from a hard and soft phase which help provide strength and ductility,
respectively. However, further optimization is possible through minor composition adjustments to achieve
near-eutectic HEAs. Joseph et al. produced a library of bulk Al CoCrFeNi samples using the DED method
x 2.1
to analyze the effect of Al-content on the microstructure and mechanical properties of alloys with near-
[182]
eutectic compositions . Figure 14A presents the XRD peak patterns of the compositions explored and
shows an increase in the B2 phase with increasing the Al content. Additionally, cast samples with the
compositions of each phase were prepared. These allowed the authors to investigate samples with single-
phase microstructures that were either purely FCC or purely B2 phase. After analyses of the phase fractions
and compressive properties of each composition, it was found that the alloys’ yield strength followed a rule
of mixtures based on the yield strength of the individual phases. This work highlights the ability of DED to
provide large sample sets that allow for rapid characterization of multiple compositions that can elucidate
strengthening trends within a system to achieve an optimal composition.

When testing the radiation damage resistance of a material, it is imperative to use bulk samples as the
damage layer thickness is typically on the order of microns, and the compositional gradient struggles to
maintain chemical homogeneity over large length scales. Additionally, thin-film-based materials typically
form nano-grain microstructures, which artificially increase the radiation damage resistance of a material,
making the results misleading compared to application conditions. Moorehead et al. printed a
[183]
compositional library of Cr-Fe-Mn-Ni alloys to assess their irradiation properties . It was found that Cr-
rich compositions showed an increase in BCC phase fraction, while Fe and Ni-rich compositions showed
higher FCC content, and Cr and Ni tended to segregate together preferentially. This trend can be seen in
Figure 14B, where the compositions with a higher Cr content show more severe segregation.
Nanoindentation was utilized as a high-throughput means to measure the effect of ion irradiation on the
hardness of each composition. Radiation-induced hardening was found in all compositions with FCC, BCC,
and FCC + BCC phases. The increase in hardness was consistently shown to be 1-1.5 GPa, with BCC-rich