Equiatomic, face-centered-cubic, high-and medium-entropy alloys were arc melted, hot-rolled to produce recrystallized sheets, and tensile tested. The alloys having the compositions CrMnFeCoNi and CrFeCoNi exhibited a strong temperature-dependent decrease in strength with increasing temperature from À196 C to 1000 C, and a relatively weak strain-rate dependence (at 10 À3 and 10 À1 s À1). Ductility did not vary inversely with yield strength; rather, when strength doubled as the test temperature was decreased from room temperature to À196 C, elongation to fracture increased by a factor of 1.5 to >60%. A high degree of work hardening, possibly due to deformation-induced nanotwinning, postpones the onset of necking and may be the reason for the ductility increase.

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