Although magnesium alloys, as the lightest structural alloys, offer significant potential for automotive applications, their applications remain limited due to their poor formability at room temperature. Since the strategies used for improving formability usually result in a degradation of strength, there are no high strength magnesium alloys showing good formability. Here we report an alloy design concept that can simultaneously provide high strength and good formability. Such designed alloy when subjected to an appropriate processing technique shows a combination of strength and formability that surpasses those of the existing magnesium alloys reported so far. The alloy design concept used in the present study is based on the utilization of alloying elements that can induce precipitation, as well as maximize the segregation of other texture-controlling alloying elements. Such developed alloy is expected to broaden the application of Mg alloy sheets, which are now starting to gain acceptance by automotive industries.

Superplasticity describes a material's ability to sustain large plastic deformation in the form of a tensile elongation to over 400% of its original length, but is generally observed only at a low strain rate (~10 −4 s −1), which results in long processing times that are economically undesirable for mass production. Superplasticity at high strain rates in excess of 10 −2 s −1 , required for viable industry-scale application, has usually only been achieved in low-strength aluminium and magnesium alloys. Here, we present a superplastic elongation to 2000% of the original length at a high strain rate of 5 × 10 −2 s −1 in an Al 9 (CoCrFeMnNi) 91 (at%) highentropy alloy nanostructured using high-pressure torsion. The high-pressure torsion induced grain refinement in the multi-phase alloy combined with limited grain growth during hot plastic deformation enables high strain rate superplasticity through grain boundary sliding accommodated by dislocation activity.

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