Alloys with combined outstanding strength and excellent ductility are highly desirable for many structural applications. However, alloys subjected to deformation at very high strain rates and/or cryogenic temperatures usually suffer from very limited ductility. Here, we demonstrate that a bulk CrCoNi medium-entropy alloy presents exceptional combination of high strength and excellent ductility during deformation at high strain rates over a wide temperature range. Full tensile stress-strain curves at a high strain rate of 2000 s −1 and temperatures down to 77 K were successfully obtained using an electromagnetic Hopkinson tension bar system attached with a cooling device, revealing high true ultimate tensile strength (σ UTS,T ) of 1.8 GPa and true strain of ~54% at σ UTS,T . These outstanding mechanical properties were mainly attributed to profuse deformation twinning. Both high strain rate and cryogenic temperature promoted deformation twinning. Grain refinement caused by deformation twinning, dislocation slip and dynamic recrystallisation added to work hardening and the excellent tensile strain.

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In this work, the virtual fields method was applied to identify the anisotropic plastic constitutive parameters for the wrought 2024 aluminium alloy. First, low cyclic tension-compression tests were conducted for the specifically designed aluminium alloy specimens on a hydraulic universal testing machine and the full-field deformations measured by digital image correlation. Then, the measured experimental data were used to simultaneously identify the constitutive parameters of the Hill 1948 yield criterion and the nonlinear kinematic hardening model based on the virtual fields method. Reasonable identified parameters were obtained. The fitting curves of the virtual work during the minimization process verify the reliability of the identification results.

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