Another issue is the relatively low yield strength (0.2–0.6 GPa) caused by the fcc structural characteristics of the alloy 14, 20, 22, 23, 24. However, such twinning is difficult to achieve at room temperature because the resolved shear stress is insufficient to reach the critical stress for twinning 20, 21. The excellent tensile properties of the CrMnFeCoNi alloy at cryogenic temperatures are mainly caused by deformation twinning 14, 15, 20. Because the properties of HEAs, including the CrMnFeCoNi alloy, correspond well with those of structural materials for cryogenic extreme-environmental applications, the successful replacement of 9%-Ni and stainless steels with HEAs can be expected. HEAs show better fracture toughness and corrosion resistance at cryogenic temperatures than conventional stainless steels used for cryogenic applications 15, 16, 17, 18, 19. 12 features strongly temperature-dependent strength and ductility, and its cryogenic-temperature strength and ductility are much higher than those at room-temperature because of its fcc structure and deformation twinning 13, 14, 15, 16, 17. Among these HEAs, an equi-atomic CrMnFeCoNi five-component alloy developed by Cantor et al. These HEAs exist as single multi-element solid solutions, have excellent thermal stabilities 5, 6, 7, are generally composed of a single phase of face centered cubic (fcc) or body centered cubic (bcc), and have properties that vary depending on the types and amounts of alloying elements 8, 9, 10, 11. New unique alloys with five or more elements present in similar portions within the alloy that have preferentially solid-solution phases have been developed as a class of high-entropy alloys (HEAs) 1, 2, 3, 4. Our results demonstrate that non-recrystallized grains, which are generally avoided in conventional alloys because of their deleterious effect on ductility, can be useful in achieving high-strength high-entropy alloys. The persistent elongation up to 46% as well as the tensile strength of 1.3 GPa are attributed to additional twinning in both recrystallized and non-recrystallization regions. These twins were retained by partial recrystallization and played an important role in improving strength, allowing yield strengths approaching 1 GPa. Considering grain size effects on the critical stress for twinning, twins were readily formed in the coarse microstructure by cold rolling without grain refinement by hot rolling. Here, we induced twinning at room temperature to improve the cryogenic tensile properties of the CrMnFeCoNi alloy. The excellent cryogenic tensile properties of the CrMnFeCoNi alloy are generally caused by deformation twinning, which is difficult to achieve at room temperature because of insufficient stress for twinning.
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