  High-entropy alloys and ceramics containing at least five principal elements
have recently received high attention for various mechanical and functional
applications. The application of severe plastic deformation (SPD), particularly
the high-pressure torsion (HPT) method, combined with the CALPHAD and
first-principles calculations resulted in the development of numerous
superfunctional high-entropy materials with superior properties compared to the
normal functions of engineering materials. This article reviews the recent
advances in the application of SPD to developing superfunctional high-entropy
materials. These superfunctional properties include (i) ultrahigh hardness
levels comparable to the hardness of ceramics in high-entropy alloys, (ii) high
yield strength and good hydrogen embrittlement resistance in high-entropy
alloys; (iii) high strength, low elastic modulus, and high biocompatibility in
high-entropy alloys, (iv) fast and reversible hydrogen storage in high-entropy
hydrides, (v) photovoltaic performance and photocurrent generation on
high-entropy semiconductors, (vi) photocatalytic oxygen and hydrogen production
from water splitting on high-entropy oxides and oxynitrides, and (vii) CO2
photoreduction on high-entropy ceramics. These findings introduce SPD as not
only a processing tool to improve the properties of existing high-entropy
materials but also as a synthesis tool to produce novel high-entropy materials
with superior properties compared with conventional engineering materials.
