Page 70 - Read Online

Xiao et al. Microstructures 2023;3:2023006 https://dx.doi.org/10.20517/microstructures.2022.26 Page 11 of 17

Figure 9. Overcoming ITE phenomena in L1 -strengthened HEAs under tensile deformation via compositional optimization and
2
structural regulation. (A) Cr doping enhanced tensile ductility at 600 °C. (B) Compact protective oxide layers introduced by the
addition of Cr (Reproduced with permission [73] . Copyright 2022, Elsevier). (C) Elimination of brittle precipitates (Heusler phases) at
GBs via a duplex-aging treatment (Reproduced with permission [26] . Copyright 2020, Elsevier). (D) Incorporation of heterogenous-
columnar grain structures by controlling recrystallization durations (Reproduced with permission [74] . Copyright 2021, Elsevier).
HEAs: High entropy alloys; ITE: intermediate-temperature embrittlement.

[76]
promote stronger electronic interaction with the host metals [Figure 11] . As earlier, a similar strategy has
[49]
been reported to improve the HE resistance because of boron segregation at GBs .

OUTLOOK AND FUTURE WORK
As a new class of structural materials, HEAs have demonstrated distinctive microstructural architectures
and promising mechanical properties, which hold significant potential for a wide of engineering
applications. As summarized above, when exposed to hydrogen and/or immediate-temperature
environments, these HEAs often display a serious premature embrittlement issue, like HE and/or ITE,
raising enormous challenges for their practical structural applications. In this situation, more fundamental
and comprehensive studies should be systematically carried out to further promote the innovation of novel
high-performance HEAs together with superior EE resistance. Here, we briefly summarize several crucial
issues and give some research directions on advanced structural HEAs with extraordinary EE resistance for
future work.

(1) Previous efforts have been primarily focused on the development of HE-resistant steels and Al
alloys [30,42,77] . The discovery of the HEAs opens a new pathway for the design of HE-resistant alloys,
especially for single-phase NiCoCr and FeCoCrNiMn. However, unlike conventional alloys, such HEA