produced by dealloying have outstanding physical properties due to their unique structure with open porous networks, [3][4][5] the undesirable coarsening phenomenon leads to degradation of physical properties over time, even at room temperature. [6][7][8] The originally proposed idea behind high-entropy alloy (HEA) with multiprinciple elements is maximizing the configuration entropy to stabilize a solid-solution alloy without undesired ordered intermetallics. [9][10][11] Many studies have suggested that HEAs uniquely possesses combined desirable properties such as a high strength and ductility paired with high fracture toughness, [12][13][14] fatigue resistance, [15] and creep resistance. [16] HEAs also show promising properties in harsh environments resisting corrosion, [17][18][19] and irradiation [20] attacks. Atomic size differences between constituting elements in HEA increase the activation energy for grain growth, and sluggish diffusion kinetics has considered as the main reason for the exceptional high strength and structural stability of HEAs at high temperatures. [21,22] The rationale behind it, the multiprinciple elements cause larger fluctuations in lattice potential energy (LPE), providing many low-LPE sites that hinder atomic diffusion. [23] Grain growth and ligament coarsening rely on the same physical background of surface diffusion. In that context, the high-entropy design in nanoporous materials has a potential for achieving an exceptional stability against the coarsening.Controlling the feature sizes of 3D bicontinuous nanoporous (3DNP) materials is essential for their advanced applications in catalysis, sensing, energy systems, etc., requiring high specific surface area. However, the intrinsic coarsening of nanoporous materials naturally reduces their surface energy leading to the deterioration of physical properties over time, even at ambient temperatures. A novel 3DNP material beating the universal relationship of thermal coarsening is reported via high-entropy alloy (HEA) design. In newly developed TiVNbMoTa 3DNP HEAs, the nanoporous structure is constructed by very fine nanoscale ligaments of a solid-solution phase due to enhanced phase stability by maximizing the configuration entropy and suppressed surface diffusion. The smallest size of 3DNP HEA synthesized at 873 K is about 10 nm, which is one order of magnitude smaller than that of conventional porous materials. More importantly, the yield strength of ligament in 3DNP HEA approaches its theoretical strength of G/2π of the corresponding HEA alloy even after thermal exposure. This finding signifies the key benefit of high-entropy design in nanoporous materials-exceptional stability of size-related physical properties. This high-entropy strategy should thus open new opportunities for developing ultrastable nanomaterials against its environment.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.

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In this work, the mechanical characteristics of high-entropy alloy Co20Cr26Fe20Mn20Ni14 with low-stacking fault energy processed by cryogenic and room temperature high-pressure torsion (HPT) were studied. X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses were performed to identify the phase and microstructure variation and the mechanical properties characterized by Vickers hardness measurements and tensile testing. Cryogenic HPT was found to result in a lower mechanical strength of alloy Co20Cr26Fe20Mn20Ni14 than room temperature HPT. Microstructure analysis by SEM and TEM was conducted to shed light on the microstructural changes in the alloy Co20Cr26Fe20Mn20Ni14 caused by HPT processing. Electron microscopy data provided evidence of a deformation-induced phase transformation in the alloy processed by cryogenic HPT. Unusual softening phenomena induced by cryogenic HPT were characterized by analyzing the dislocation density as determined from X-Ray diffraction peak broadening.

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