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Precipitation strengthening is believed as an important strengthening method that optimizes the strength of alloys. Herein, the possibility of precipitation strengthening is demonstrated by introducing the intermetallic (Cr, Si)‐rich σ phase in the novel FeCrNiSix MEAs system. It is found that simultaneous enhancement in strength and work hardening can be attained by adding Si element in the FeCrNi MEA. Specifically, the FeCrNiSi0.2 alloy realizes a good balance of strength and ductility due to the precipitation of ultrafine‐ or even nanoscale‐sized σ phase. Moreover, quantitative analyses are conducted to assess the underlying strengthening mechanisms.

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Bulk large-gradient nanostructured NiCoCrFe high-entropy alloys with millimeter-scale gradient layer were prepared by supersonic Taylor impact. The microstructure evolution over a wide range of strain rates (10−3–105/s) was characterized, and the formation mechanism of nanocrystals with well-defined boundaries at high strain rate (>104/s) was identified to be the emerging, thickening, and mutual intersection of lattice rotation bands, high-density dislocation bands, and deformation twins. This Letter not only reveals the deformation mechanisms of high entropy alloys under a wide range of strain rates but also provides an idea that could be applied to the preparation of bulk gradient nanostructured materials.

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