Ever-harsher service conditions in the future will call for materials with increasing ability to undergo deformation without sustaining damage while retaining high strength. Prime candidates for these conditions are certain high-entropy alloys (HEAs), which have extraordinary work-hardening ability and toughness. By subjecting the equiatomic CrMnFeCoNi HEA to severe plastic deformation through swaging followed by either quasi-static compression or dynamic deformation in shear, we observe a dense structure comprising stacking faults, twins, transformation from the face-centered cubic to the hexagonal close-packed structure, and, of particular note, amorphization. The coordinated propagation of stacking faults and twins along {111} planes generates high-deformation regions, which can reorganize into hexagonal packets; when the defect density in these regions reaches a critical level, they generate islands of amorphous material. These regions can have outstanding mechanical properties, which provide additional strengthening and/or toughening mechanisms to enhance the capability of these alloys to withstand extreme loading conditions.

High entropy alloys (HEAs) have emerged as a new class of materials that can exhibit superior mechanical properties to the conventional alloy systems. Therefore, they are promising candidates as the next generation structural materials. As the studies into the HEAs deepen, the original proposal of equal concentration of each element while remaining a single phased structure has been expanded and new opportunities start to emerge. Here we briefly discuss several future directions for HEAs which include fundamental questions such as chemical short-range order and synergistic strengthening mechanisms, as well as HEA’s potential applications under extreme conditions such as high-temperature and cryogenic load-bearing, impact protection and kinetic penetrator.

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